The Public Understanding of Genetics - where next?

Dr. Jon Turney,
Wellcome Fellow in Science Communication, Department of History, Philosophy and Communication of Science, University College London, Gower Street,
London WC1E 6BT, GREAT BRITAIN

INTRODUCTION

As the human genome project gathers momentum, there is wide agreement that a broad effort to improve public understanding of genetics will be needed to underpin public debate about the applications of the new genetics. Before attempting to bring about such an improvement, it would be helpful to have a clearer idea where public understanding of genetics now stands. This paper considers what we already know about the public understanding of human heredity and genetics, and what we should try to find out.

I first ask what meanings "public understanding of genetics" might have, in the light of recent discussion and research about the public understanding of science more generally, and then try to sketch a range of possible elements of understanding of genetics. Then I indicate which part of this range is the main focus here, and go on to review a number of areas of inquiry which seem helpful in assessing what we already know. Any inquiry of this kind will need to be multidisciplinary, and each of the areas I sample - surveys of public understanding and attitudes, history of science, educational research, and work on the mass media and popular culture - has something to contribute to the full picture.

Finally, I try to identify the main gaps in the work reviewed, and consider where further research in this area might be focused.

WHY PROMOTE THE PUBLIC UNDERSTANDING OF GENETICS?

One problem in advancing the wider debate about the public understanding of science, conveniently dated from the Royal Society's report of that title in 1985 (Royal Society. 1985), has been that each of the three terms in the key phrase, "public", "understanding" and "science" needs unpacking in some detail when any particular problem must be addressed.

Most academic writers in this area now emphasise the importance of considering "knowledges in context", rather than some abstract ideal of public understanding of science in which the task implicitly set for the laity is to learn to reproduce scientific accounts of situations or phenomena at whatever level they are capable of (Wynne, 1991). In practice, people try to acquire "science for specific social purposes"(Layton et al, 1993). And as Joan Solomon puts it, "scientific knowledge needs to be partnered with complementary social understandings, even at the expense of conceptual purity, if it is to become usable as citizen knowledge" (Solomon, 1992).

These comments apply to genetics as much as to any other area of science. As Rayna Rapp has repeatedly emphasised in her studies of genetic counselling from a cultural anthropological point of view, "while the language of science claims to be universal, it must, in fact, confront the local idioms with which diverse groups and individuals respond to its powerful messages" (Rapp, 1988). In a later paper drawing on the same material, she elaborates on how the unequal encounter between prior beliefs and scientifically-sanctioned ideas about genetics is managed, emphasising the "discursive work" that the construction of a scientific view of heredity entails: "Not only must popular meanings of hereditary transmission be suppressed in favour of scientific ones; scientific meanings must also be made sufficiently accessible so that patients (in this case pregnant women and their supporters) can act upon them" (Rapp, 1992, and forthcoming). At their simplest, such ideas imply that we pay close attention to such questions as who might need to know what, for what purpose, and who is defining their need and prescribing how it might be met? I return to this point at the end of the paper.

Here, I will revert to the general question of why genetics might be thought important enough to promote a general understanding of the subject. At one level, the answers are obvious. Genetics, or at any rate reproduction and heredity, are of compelling interest to us all, and tap deep currents of personal feeling. This has long been recognised by scientists in the field who have had any contact with the public. But if interest is easy to establish, understanding does not necessarily follow, partly because the science has changed so much in the last few decades. The latter-day concern about public understanding of genetics arises to some extent because the flow of novelties - new information, new technological capabilities, new calls for individual and institutional decisions - is incessant, and appears to be accelerating. What forms does this concern take?

In discussion of genetics, and specifically human genetics, the view that improvements in public understanding are desirable is very widespread. At its grandest, it gives rise to statements like Nancy Wexler's that "rather than slow the science, we need to accelerate the creation of a social system that will be more hospitable to new information about our genes, our heritage and our future"(quoted in Cooper (ed), 1994).

This view seems to have three main motives. One is that, as the human genome project bears fruit, more people will need to make sense of information about the results of screening tests, for example. As the recent Nuffield Council on Bioethics report put it; "If an individual is to be well enough informed to be able to give consent to genetic screening, he or she needs to have some general understanding of genetics. This means that the public as a whole needs to have a greater knowledge and awareness of the genetic processes that can affect us all" (Nuffield Council on Bioethics, 1993).

Aside from individuals' ability to give informed consent (or, presumably, decline to do so), there is a wider need for understanding to inform policy-making in this area. Again, this is highlighted in the Nuffield report; "A broad public understanding of the scientific basis of medical genetics is essential if informed public policy decisions are to be taken about the introduction of genetic screening programmes."

Finally, there is an interest on the researchers' part in a different facet of policy-making, the regulation and oversight of work in the laboratory and its application - from environmental release of genetically modified organisms to protocols for trials of human gene therapy. At this level, there is concern about improving public understanding to ensure that the research is permitted at all. This concern is quite prominent in some areas of the life sciences. As Sir Ralph Riley put it, succinctly, "there is often insufficient understanding of genetics for rational judgements to be made of its effects" (Riley, 1993), although the record suggests that when there are particular threats to research the scientific community can be very effective at mobilising to fight them off, as shown by the Parliamentary debate about embryo research , for example (Mulkay, 1994).

WHAT NEEDS TO BE UNDERSTOOD?

These suggestions about why improved public understanding would be a Good Thing also imply what might count as improved understanding. But this is actually a more complex matter than the Nuffield prescription, for example, suggests. Even taking the science on its own terms, there are a number of elements which might enter discussion of public understanding. The definitions below are not intended to be watertight - and are certainly neither exhaustive nor mutually exclusive - but they may give some signposts for the discussion. Although my main interest here is in human genetics, most of this discussion will be general, as it is an open question at this stage whether there is any separation in the public mind between ideas about human inheritance and about inheritance in any other species.

1 - Mendelian inheritance and classical genetics.

One can grasp the rudiments of inheritance at an abstract level, in terms of resemblance and difference between individuals and generations, the nature of sexual reproduction, the patterns which can be discerned in inheritance of particular traits, and the ways these can be understood. A scientific understanding here turns on the idea of genes as (material) Mendelian factors, as they were conceived in roughly the first half of this century. The concept of gene at this level is perfectly adequate to account for independent inheritance of different traits, the difference between dominant and recessive alleles, genotypic/phenotypic distinctions, penetrance and X-linked inheritance. With terms like these, suitably translated, a genetic counselling session, for example, can be used to convey an understanding of risks of recurrence of some condition without ever mentioning the way genes actually work.

Explanation is at the level of cell biology, rather than molecular genetics. This kind of account of genetics has been readily accessible to an educated public for almost 90 years, with the first full accounts of the "atomic theory" of inheritance appearing remarkably soon after the rediscovery of Mendel's laws in 1900 (Thomson, 1908). Into the 1980s, standard texts on genetic counselling could still be restricted almost entirely to this level, describing karyotyping, chromosomal aberrations, and the human gene map in terms which required almost no mention of DNA (Kelly, 1980). Most popular accounts of the basis of inheritance begin at this level (Pierce, 1990), though those for other audiences may no longer do so (Holtzman, 1989).

2 - What are genes made of?

The first entry into modern molecular biology. Introducing the idea that genes are made of DNA, and the manner of its self-replication, gives a different framework for understanding the mechanism of the ideas introduced in classical genetics (Waters, 1994). One can begin to visualise how information is preserved, reproduced and transmitted. The notion of mutation acquires a molecular correlate, and the various new technologies of screening can be explained in terms of identifying, amplifying or tagging specific base sequences.

3 - What does DNA do?

It is possible to grasp the idea that the genes are made of DNA without having any notion of how the information it encodes is read or used, so it seems plausible to define this part of the molecular biological story as the next level. This would include transcription and translation of DNA messages, the relations between linear information and three-dimensional structures of proteins, and the way proteins are used in the cell. This set of ideas might thus be adequate to give an account of the molecular basis of sickle-cell anaemia, say, or cystic fibrosis. These two areas are the stuff of molecular genetics textbooks, which may cover the whole field (Lewin, 1990) or may focus on the new experimental techniques in particular (Watson et al, 1992).

4 - Genes and environment.

So far, the implied exposition has ignored the role played by environmental factors in development, and in gene expression in the grown organism. The complexities of these interactions are obviously an important part of any realistic understanding of genetics. The importance of understanding this is increasing as molecular genetic techniques are applied to conditions which are not (or only rarely) simply genetically determined - breast cancer as opposed to Huntington's disease, for example. Huntington's is caused by a single, dominant gene, and the presence or absence of the variant allele is a reliable predictor of risk. It is quite a different proposition counselling patients in families which carry the altered allele of the newly-discovered gene BRCA1, which confers an extremely high lifetime risk of early-onset breast cancer, but still only accounts for two or three per cent of cases of the disease (Turney, 1994b).

5 - The environment includes other genes.

The complexities of interaction include interactions between genes and their effects in the cell or more widely. The modulation of gene action by other genes and gene products is understood in detail in only a few cases. Many more are likely to be described in the next decades, reinforcing our sense that the whole genome is part of the environment of each individual gene within it. At the least, one needs to know that, depending on the circumstances, many genes may contribute to the same pathology, either all at once or in different cases; that the same pathology may be wholly or partly caused by genes in some cases but have quite different origins in others; that the same gene can contribute to several different pathologies, or none, in different individuals.

Some prescriptions for public understanding suggest that we need more emphasis on these complexities, to counter an historic legacy of simple Mendelian exposition. Thomas Fogle, for example, asserts that "the public view of the genotype-phenotype relationship is oversimplified and does not capture the complexity of molecular events as revealed by modern biology" (Fogle, 1987). He argues that this leads to exaggerated expectations about the efficacy of potential new technologies; "talented high school science students believe that you can easily cut and paste the genome as if genes were parts that can be rearranged and expect a precise outcome". However, as he emphasises, "with the advent of modern knowledge about jumping genes (transposons), coding regions (exons) that can be spliced together in more than one combination to produce multiple gene products, and nucleotide sequences that are part of two reading frames (overlapping genes), genes can no longer be visualised as simply a series of fixed, discrete units".

6 - Evaluating the medical model.

Finally, one might take the most sophisticated kind of (still strictly scientific) understanding to be one which tries to place the current emphases of biomedical genetics in the contexts of wider debates within biology. There is a view, for example, that the human genome project is the culmination of a 200 year-old reductionist research programme in biology, but a culmination which comes at the same time as the limitations of that research programme for biology - and even more so for medicine - are becoming apparent (Tauber and Starker, 1992, Lewontin, 1994). Richard Strohman has argued at length that the prevailing medical genetic research paradigm, which in his view dominates much professional and lay discussion, is out of step with many developments in mainstream biology. In his view; "applied biomedical efforts centred on molecular genetics have diverged from fundamental research issues in population genetics, in cell and developmental biology, and in molecular biology itself. This cleavage between applied medical sciences and basic research biology is potentially dangerous to the public health" (Strohman, 1993).

Whatever the merits of this view, it underlines that there is no simple scientific consensus about what it is the public might find it helpful to understand beyond the basics. Understanding here becomes a matter of making a judgement about the significance of some of the facts of hereditary mechanisms which would fall under one of the earlier headings. This may in some ways be an unattainable ideal in terms of wider public understanding, but as genetic research makes more impact on discussion of policy and planning for health services, for example, it is not an ideal which can be set aside altogether.

This, then, is one way of unpacking "understanding" of the science of heredity. But there are yet other aspects of understanding which need to be brought into any full discussion. The first few elements defined above fall into what Collins calls technical understanding (Collins, 1993a, b). He contrasts this with reflective understanding of various kinds, concerned with the nature and process of science. In this context, it might entail some acquaintance with the history of the science and technology underlying the knowledge outlined at different levels above, with how we came to know what we know. This would certainly seem essential for the higher levels of discussion. Taking a view on the kinds of controversy highlighted by Strohman, for example, must depend on having a sense of what kinds of research practice are involved in the different areas of science he discusses. More generally, helping those outside particular scientific communities put new information in context must depend on their general sense of what kind of claims it is legitimate to make, on what experimental basis. In a field like genetics, where the pace of advance is currently so swift, the argument for understanding "science in the making", as Shapin puts it, is perhaps more persuasive than in areas where the knowledge base is more stable (Shapin, 1992).

Finally, all of this work also has a social history, which is plainly a major influence on public understanding and attitudes. So a full picture of human genetics entails some knowledge of the history of the eugenics movement, for example (Kevles, 1985), or perhaps of the XYY controversy of the 1970s (Green, 1985), or the debates over sociobiology (Lewontin, 1984, Kitcher 1985).

This is a formidable agenda. But any serious effort to improve public understanding of genetics needs to be located somewhere here. While most such efforts will inevitably fall far short of including all these aspects, it may help to classify them in terms of the kinds of ideas outlined above. Plainly, any one of these elements can be treated sketchily, or in great detail, and there are obvious trade-offs between them in any given text. The works I have been citing are a mixture of technical, historical and popular accounts, and each of these have different ambitions and audiences. The 800-odd pages of Lewin's Genes IV, for example, cover material which another book with quite different aims might dismiss in a few pages, or put in a quite different context. (Note also that the latest, fifth edition of Lewin's text, surely the last which can be published as a single volume, has expanded to 1300 pages). It is, of course, more common for popular books to try and include something of all the elements I have outlined. Again, this can be done as simply as possible (Hodson, 1992, Jones and Van Loon, 1993, Gonick and Wheelis, 1983), or at considerable length (Jones, 1993, Tudge, 1993, Turney, 1993).

The complexity of the subject means that the entry-cost to join even an introductory public discussion is rather high, as an analysis of two linked articles about the human genome project in Time magazine in 1989 shows (Mertens and Hendrix, 1990). As they report, this feature in a mass-circulation news magazine with extensive journalistic resources makes considerable demands on the reader. The two articles (one on the science of the project, one on ethics), cover eight pages and use at least 64 technical terms from genetics, biology and chemistry. "These terms range from sperm, egg, cell, nucleus and chromosome to the more esoteric - oncogenes, restriction fragment length polymorphisms, retrovirus and eugenics. Many of the basic terms are not defined or explained, while the more esoteric ones are. In addition to the many concepts one must understand to grasp the thrust of the two articles, the reader encounters the mention and/or brief discussion of 18 genetic diseases or defects." Compare this with a short article which tries to offer a "Guide to the jargon of genetics", recently published in The Independent, which defines a mere 15 terms (Wilkie, 1994).

All of this underlines how many choices have to be made in designing any effort to contribute to public understanding of genetics. Although I am only citing printed sources here, this obviously applies whatever medium might be used. But while this range of choice must be acknowledged, it is impractical to confront the full range much of the time. In reviewing what we already know about public understanding of genetics, I will narrow the context. My main interest will be in understanding which might be relevant to making use of the results of genetic testing. But I still want to generalise to some extent.

The advent of genetic testing for a much wider range of disease-related alleles than has been possible up till now raises particular new problems of education and understanding. Existing experience in the use of such tests is in clinical contexts, principally genetic counselling. But it is also worth thinking about educational efforts outside these existing contexts, for at least three reasons. First, most genetic counselling, and most studies of counselling, have focused on reproductive decision-making - and we now look toward a time when much, perhaps even most, genetic testing will relate to personal risk rather than reproductive risk (obviously the distinction is not clear cut). Second, clinical counselling may not be a viable model for the way information is going to be acquired. There may simply be too much testing for all of the results to be discussed with trained counsellors. And new models of delivery are likely to emerge, possibly commercially driven.

There are two extremes on the spectrum of models for how genetic tests might be deployed. At the traditional end is the normal medical procedure of a referral to a medical specialist, the taking of samples, and a further appointment in a matter of days or weeks to discuss the result. At the other extreme might be "high street" cholesterol screening, either in a pharmacy, or using a kit bought off the shelf and taken home.

Gene technology may well move away from the clinical end of this spectrum relatively rapidly. There is serious commercial interest in both Europe and the United States in developing mass-produced devices which will be able to test blood or other tissue samples for hundreds of diagnostic DNA sequences at once, and produce an instant computer readout of the results. Boehringer-Mannheim in Germany are spending £100 million developing immunofluorescence and laser scanning techniques pioneered at University College London to do just this. In the US, the Department of Commerce is backing a five-year, $145 million programme of competitive awards to develop commercial DNA diagnostics (Ekins, personal communication, Anderson, 1994).

The first generation products which emerge, perhaps as soon as the late 1990s, are likely to be portable diagnostic cards, which will find a place in surgeries and clinics. But it may well be that subsequent generations, or devices to test for one or a few particular conditions, could become buy-use-and-throwaway items for anyone. The technical details are not important. What is important is to recognise that the human genome project is a technology forcing project, and it will produce a new set of technological capabilities as well as a collection of DNA maps and sequences. So the home cholesterol kit is an extreme example at the moment, but is a useful model for thinking about the kinds of problems which widely diffused innovations in genetic testing technology will pose.

Finally, the new genetic tests will be less and less often concerned with simple Mendelian conditions, like the classic cases of sickle-cell anaemia or Huntington's disease. They will involve susceptibility to multi-factorial conditions, or conditions which can have different causes in different people. They will be about risk factors and probabilities, not yes or no answers. And they will be about very widespread conditions, like cancer or heart disease, and so will potentially be applied to very large populations (Rennie, 1994, Turney, 1994a).

For all these reasons, it is worth thinking about a wider educational effort in human genetics, which will try to prepare people to assimilate and use new information in ways they feel comfortable with. Such an effort, if successful, would also be of some benefit to more specific counselling efforts - a rising tide lifts all boats. This is the kind of effort which I will try to keep in focus in what follows. Although it could in principle (and perhaps should) include all the elements of technical understanding I have outlined, as well as the other areas indicated, in practice one might begin by focusing on the first few elements, to see what progress might be made.

In any case, so far as existing research goes, most studies have been restricted to these first elements. So the majority of what follows necessarily follows suit. The rest of this paper looks in turn at a number of areas of inquiry which may yield data on existing levels of public understanding in this area, or be a source of ideas about possible misconceptions about human heredity.

WHAT DO WE KNOW ABOUT WHAT WE KNOW?

a) Surveys

A number of surveys of public knowledge and attitudes have included relevant questions. They were fielded for different reasons at different times, but some of the results are suggestive. They mostly give an indication of consciousness of key terms, rather than probing understanding in any depth, as well as giving some indications of how the possibilities of biotechnology and new reproductive technologies are seen by a somewhat wary public.

Taking the earliest first, Winstanley carried out a small-scale survey of university students in the mid-1970s, to find out "who knows their DNA?". This gives an indication of how widely knowledge of the new genetics had diffused twenty years after the double helix, among those who had benefited from advanced secondary education (Winstanley, 1976).

She asked 331 students to choose from five possible definitions of DNA, and to consider ten other terms, or named scientists, and simply say whether they had heard of them. The results compare biology students with those taking non-biological science, arts or social sciences (see Table 1).

Nearly one third of the non-science students had never heard of DNA, and two-thirds had never heard of the double helix. But a majority of those who had heard of it could define it correctly. Nearly everyone (98 per cent of the non-scientists) had heard of genes, though a significant minority thought they were only found in the sex cells of adults.

Table 1: Students studying - (total responses 331)

"Genetic engineering" was recognised by more than half of respondents in all subjects, though still some way behind DNA, while more had heard of Mendel than Watson, Crick or Wilkins. Other findings showed how scientific terms can be recognised without their interconnections being understood. For example, around one sixth (57) of the respondents agreed with the statement that "genes are stable and never alter", even though more than two thirds of this group also knew the word "mutant".

Biology education at school seemed to have no measurable effect on knowledge of these terms, with university students who took biology A-level before studying for an arts or social science degree scoring no better than their fellows with no school biology. This is consistent with the non-biology students reporting that TV (for 60 per cent) was their major source of scientific information.

A decade later, Lucas reported responses to some "scientific" questions included in a MORI poll in the UK in mid-1986 (Lucas, 1987). Some were biological, including:

"When we look at animals and plants we find many similarities between parent and offspring. What is it in animal and plant cells that ensures that offspring have many similarities with their parents?"

This question, which assumes that "cell" is a meaningful term, yielded the following responses from the general population sample of 1033:

Genes - 52 (%)

Chromosomes - 7

RNA/DNA - 4

Other - 4

Don't know - 34

Among the small portion with degree or diploma level education (in any subject), the percentage answering either genes or chromosomes rose to 87%. Again, the results seem to indicate that around a third of this sample were unable to recall any idea about what is going on.

Next, the major national survey of public understanding of science in mid-1988 included a question on genetics in a section devoted to a "knowledge quiz" (Durant et al, 1989) Again, this was a representative adult sample, and they responded as follows:

Doctors tell a couple that their genetic make-up means that they've got a one-in-four chance of having a child with an inherited illness. Does this mean that.

i) If they have only three children, none will have the illness?

Yes - 4.9 (%)

No - 84.2

Don't know - 10.7

ii) If their first child has the illness the next three will not?

Yes - 9.3

No - 80.3

Don't know - 10.3

iii) Each of the couple's children has the same risk of suffering from the illness?

Yes - 82.1

No - 9.6

Don't know - 8.0

iv) If their first three children are healthy, the fourth child will have the illness?

Yes - 8.6

No - 80.3

Don't know - 10.9

This is a striking finding from a survey which was widely represented as disclosing public ignorance of many basic aspects of science and technology. The answers are mostly correct, and consistent with one another. They might suggest that the characteristics of simple Mendelian recessives are widely and well-grasped, in contrast to the answers to many of the other, less elaborate quiz questions (for example, 65 per cent agreed with the suggestion that radioactive milk can be made safe by boiling it). Only three questions out of fourteen, on whether the centre of the earth is very hot, whether sunlight can cause skin cancer and whether hot air rises, elicited a higher proportion of right answers (up to 96 per cent for the last item). The pattern in the United States - where Miller's group fielded the same questions, was different, with the genetics question still well answered (71.1 per cent correct responses) but not that much better than a number of other items (Durant and Evans, 1989). Nevertheless, this appears as an encouraging result, on both sides of the Atlantic.

This encouragement is reinforced on examination of an earlier, and much more detailed survey of US high school and college students carried out in the 1970s for the Biological Sciences Curriculum Study (Hockman et al, 1978). Almost 80 per cent of the respondents in this study answered correctly when asked whether it was true or false that:

"If a couple has a one in four chance of having a child with a genetic disease - and their first child has the disease - then they know that they can have three healthy children before the disease will occur again."

As with the later survey, though, it may be that the form of the question means that it is a better indicator of understanding of simple probability than of genetics per se.

This impression is reinforced by responses to other questions in the BCSC survey. For example, for the question whether it is true or false that:

If two parents each carry a gene for sickle-cell anaemia but neither has the disease, their chances of having a child with the disease is 50:50;

the correct answers fell sharply to less than one third of the respondents.

Finally on knowledge, the largest survey so far is the "Eurobarometer" effort to track public knowledge of, and attitudes toward, biotechnology across the European community. This inquiry was first mounted, on behalf of the European Commission in 1991, and repeated in 1993. This is a highly elaborate exercise, involving 12,800 adults in 12 countries, and covering a wide range of opinions about the biotechnology and its future uses, government regulation, and credibility of information sources. Once again, a reasonably high background knowledge of some elementary facts about heredity is indicated, but there are substantial minorities who choose the wrong answer, or don't know.

These are the main "knowledge" data. Other surveys exist, but they mostly focus on attitudes (Lemkow, 1993). These may offer indirect evidence about knowledge or understanding, as the questions must make sense to elicit any response, but they do not tell us what kind of sense they are making. (Martin and Tait, 1993, Turney, 1994a, Yearley, 1992).

b) Historical ideas about inheritance.

The historical development of ideas about heredity, difference and, ultimately, human genetics, is a useful indicator of notions which may still have a role in popular conceptions of the subject. Of course, there is no reason to suppose that the development of an individual's ideas today recapitulates those held in earlier times, though some may draw similar conclusions from similar phenomenology. But old ideas may persist in language, metaphor, folklore or popular culture, and an awareness of their history may help alert us to their contemporary resonance.

There is little to be gained here by summarising individual works, which each themselves offer composite accounts of the history of ideas. A proper historical discussion, avoiding anachronism, is a major undertaking. The distinction between inheritance and development is relatively recent. Indeed, the notion of heredity as a causal factor in an organism's make-up was not clarified in the sense we now recognise until intense discussions of the influence of "the hereditary" on disease among French physicians in the 1870s and onwards - and there was little popular discussion of the idea in Britain for another hundred years (Lopez-Beltran, 1994). But there are a number of aspects of pre-Mendelian ideas about inheritance and development worth noting (Stubbe, 1972, Dunn, 1965, Jacob, 1976).

The oldest ideas presumably derived from experience with domesticated plants and animals, which goes back several millenia. Sophistication in their propagation also goes back a long way. For example, the Assyrians in early 800s B.C. were pollinating date palms artificially. Stubbe summarises:

"The presence of domesticated animals, cultivated plants, and above all, the appearance of new races and varieties must be considered as the first results of what were perhaps at first unconscious attempts to breed and cultivate genetically; it is certain, however, that such attempts were undertaken consciously as time went on. There is no doubt that the selection of economically valuable variants or of the products of spontaneous crossings among wild stocks (tough rachis, uniform germination, size of the grains, etc.) and their isolation and propagation, were at first the all-important considerations. In this way it was learned that desirable features as well as undesirable ones were preserved in subsequent generations; that is to say, they were inherited. It must also have been recognised in those early stages of development that this process was true of human beings as well.

Stubbe also details various religious precepts. The Hindu prescriptions for a happy life imply a notion of heritable diseases, for example. He relates the oft-cited Old Testament story of Jacob producing speckled cattle to order to exemplify belief in inheritance influenced by environmental factors or "evil imprinting of the unborn". He then moves on to the Greeks.

There is general agreement that classical ideas stem from the Hippocratic or Aristotelian traditions. The Hippocratic doctrine of pangenesis implied that there was a contribution from both male and female semen, and that semen was drawn from all parts of the bodies of both parents by a blending of the humours, warmed during copulation. "The offspring could neither reproduce one nor the other parent precisely, but nor could it bear no resemblance at all. The similarity with respect to any one part was said to correspond to the quantity of semen from each parent for that part. In organs where the father contributed the greater amount, this would dominate the maternal contribution and that organ would resemble the male, and conversely for organs where maternal semen had the greater volume." (Russell, 1986). Elements of pangenic theory persisted until the late 19th century, forming the basis of Darwin's theory of heredity. Indeed, some historians consider that nothing of note happened in the history of theorising about heredity between the Hippocratic era and Darwin (Moore, 1993).

Aristotle, in contrast, believed that only males produce semen, with the female contributing menstrual blood. Both were derived from the parental blood, with the semen playing the major role because of its origin in the more perfect male, and hence its greater "innate heat". The form of the organism was transmitted through the blood, which carried nourishment to all the organs.

Little of this theory was of much direct use (or, often, interest) to practical animal breeders of the kind followed by Russell. Their ideas came from a wider variety of sources. One was the analogy with the ideology of human breeding in the sense of "good breeding", as a justification for aristocratic inheritance. These ideas, and their associated notions of pedigree and blood lines are still with us, in both animal breeding and lay ideas of human inheritance.

Another set of beliefs present at some periods in considerations of animal mating was astrology - whether the time was propitious for producing offspring with desired characteristics. "To the seventeenth-century breeder, particularly, astrological conditions and the imaginative powers of the breeding organisms at the time of copulation seemed as significant as any other environmental constraint on the quality of the offspring". (Russell, 1986). It is worth noting that astrology offers (among other things) an alternative account of the origins of human character, as determined by star signs and planetary configurations - and one which is still very much alive in popular culture.

Animal breeders (and presumably others) also tried to reckon the influence of a host of other factors, environmental and circumstantial. Russell's discussion of selection by phenotype in animal breeding is instructive:

"The implication of such selection must be that the offspring are expected to inherit the desirable parental characters. Until recently, selection by phenotype has often been misguided because the degree to which any character was strongly inherited, as opposed to largely determined by environment and management, has been impossible to determine. Such a distinction between an inherited component of character and a non-heritable, environmentally determined component would have been meaningless to many earlier breeders. As far as they were concerned, the parent animals passed on the characters that they exhibited at the time of copulation. All such characters were considered potentially heritable. Therefore many environmentally acquired characters were regarded as transferable, so that high condition was often favoured, for instance, because the condition was believed heritable. Similarly, age at copulation was often regarded as critical since the parents were thought to confer the weaknesses and conditions of their age upon their offspring. In many cases one sex, usually the male, was seen as critically important, so that parental selection was applied vigorously to one parent type only." (p15) (original emphasis)

So much for formal historical studies. Another valuable source of historical notions about heredity may be popular works which try and convey modern ideas to lay audiences. Such works await a full study, but a few useful examples are to hand. One recent popular guide to genetics, by Hodson, lists seven "devastating misunderstandings" of the past and suggests that at least three and probably four are still alive today in the West (Hodson, 1992). The seven are:

- That the father is more important to heredity than the mother, as in the Aristotelian scheme, a belief which the author suggests lingers on, and not only among racehorse breeders;

- Preformation theory, which is long discredited, but "maybe the old idea has not quite disappeared. Do people who say, 'Ah, he's got his father's nose', perhaps believe in some way in the transmission of an actual miniature nose?"

- That the mother is responsible for the sex of the baby - seen as still in evidence in lay ideas of boys or girls "running in families";

- Mutants as the wrath of God - seen as a source of the shame and guilt which often still attend the birth of a child with a heritable defect;

- Spontaneous generation - no longer with us;

- Inheritance as blending, from the Hippocratic tradition;

- Inheritance of acquired characteristics, which she tells us "is the most tenacious misunderstanding of them all, being still widely believed by the general public even though a hundred years have gone by since it was proved to be impossible". Hodson unfortunately does not go into the evidence for the prevalence of this belief.

Her list may be compared with one from a rather different work from sixty years earlier. Wells, Wells and Huxley's comprehensive three-volume popular treatise on The Science of Life tried to review the whole of the biological knowledge of the time, including (pre-molecular) genetics (Wells, Wells and Huxley, 1930). At the close of their exposition of current knowledge of genetics, in which they hold the genetic map of Drosophila to be the highest achievement of the science to date, they detail "certain beliefs which are widespread enough among the general public. They may truly be called superstitions since they are without any of the ample basis in facts which underlie breeders' beliefs on inbreeding and outcrossing".

Their run-down of these begins with telegony, or "infection of the germ"; the idea that the first male to which a female is mated has an influence on later offspring sired by another male. Related to telegony is the converse idea, that the quality of a male's later offspring can be affected by an earlier mating with a poor quality female. They cite various examples of alleged telegony in animals, but also say that "curiously enough, the belief does not seem to be strongly or widely held about the matings of the human species".

Their second superstition is the belief in "maternal impressions", which they illustrate with the story of Jacob's cattle from Genesis. They suggest that "today it is in the field of human reproduction that this superstition is strongest". They continue at some length to explain why there is no possibility of some impression on the mother being passed to her (animal or human) offspring, suggesting that the authors did indeed feel that the belief was widespread.

Then Wells and Huxley continue with a variety of unwarranted beliefs which they maintain are found among breeders, including myths about sex determination, the existence of a quality of vigour, or the idea that sickly parents have poor quality offspring. They emphasise that this has been refuted by experiment, and that "so long, it appears, as the organism is not so feeble as to be incapable of reproduction, the genes which it transmits are working genes and their shuffling and assortment goes on in the usual way" (all volume 2, pp331-335).

Significantly, the inheritance of acquired characteristics is tackled at length in a separate section, and although the authors clearly oppose the idea, they do not take for granted that the reader of the 1930s can be convinced that the notion should be dismissed. Plainly they recognised that the scientific consensus was not yet complete.

Examples like this give an indication of the ideas which some earlier authors believed they had to argue against. Such texts may permit indirect inferences about the state of popular understanding of heredity through this century - in the absence of the kind of survey data we have for more recent years. For instance, Thomson's Heredity from 1908 has a whole chapter on ideas taken to support the existence of telegony and maternal impressions, and a further chapter discussing inheritance of acquired characteristics (Thomson, 1908). So far as my immediate concern here goes, they are undoubtedly a useful supplementary guide to lay ideas which may still have some currency.

c) Educational research

There are a number of educational studies which try to test the effectiveness of formal teaching of genetics, in terms of the accuracy of students' knowledge before and after instruction. They establish that, when taught, genetics is found to be one of the more difficult areas of biology to understand (Johnstone and Mahmoud, 1980). It is suggested that the level of abstraction of the ideas means that school students need to be old enough to have acquired formal reasoning skills rather than being restricted to the concrete operational reasoning (in the Piagetian scheme) of their younger counterparts (Walker, 1980, Gipson, 1989, Lawson and Thompson, 1988, Gardner, 1993).

An unusually detailed example of this kind of assessment is a study of 48 15 year-olds in Australian schools (Hackling and Treagust, 1982). This study defined 18 propositions to capture what the authors claimed students ought to know about (classical) genetics after their teaching sessions. The overall impression from the results is that the actual lessons made little impression. The items where student comprehension was good, like the facts that inheritance and reproduction occur together, that children's features come from their parents, that the genes for these features are in the gametes and that each parent contributes to a mixture of features in the next generation, tended to be those which "could have been developed from observations of patterns of inheritance within the students' own families."

In contrast, ideas included in the teaching but which did not relate so readily to concrete experience, like alternative forms of genes and dominance relationships, were comparatively poorly understood. Other propositions which failed to get across to most of these pupils included the existence of polygenic traits (which was not often taught), the influence of chance on an individual's make-up, and the fact that Mendelian ratios only apply to large populations, not families. There was also little understanding of the origins of gametes in meieotic division, or of the genetic equivalence of different body cells.

As well as studies like this, there are a smaller number which focus on what one might call alternative conceptions of heredity. The distinction is not completely clear cut, but arises because the last 15 years has seen a large effort to explore children's prior ideas about "scientific" topics before they are taught them in class. This effort has been heavily weighted towards the physical sciences (dynamics, electricity, energy) (Driver, 1988, Carmichael, 1990, Mintzer, 1989). Indeed, at least one author has suggested that there is little evidence for early misconceptions about biological science analogous to those recorded in physics, although as this conclusion is based on interviews with just three elementary school children it is scarcely robust (Lawson, 1988). In any case, there are other studies which focus on biological questions, and some which explore ideas about heredity specifically (Stuart, 1983).

Some studies simply ask how much students knew before they were taught about evolution or heredity, and typically find the answer is; not much (Deadman and Kelly, 1978). One which probes in more detail is Kargbo et al's early study on children's beliefs which involved a small group (32) of Canadian children aged 7-13 (Kargbo et al, 1980).

Individual, half-hour interviews were designed to find out three things:

a) to what extent did these children distinguish between environmentally produced characteristics and purely inherited traits in living organisms?

b) to what extent did they employ probabilistic thinking to predict an offspring's inherited characteristics from observing the characteristics shown by the parents?

c) what types of explanations did they use to support the predictions made?

The children had to answer questions about five stories - three about acquired characteristics (usually mutilations rather than adaptations), two about probabilities. The stories covered animals (dogs), plants and people.

The results indicated that almost half, even among the older children, believed that some environmentally induced characteristics could be inherited.

They were more likely to believe this of animals and people than trees, and inclined to think it less likely if there was a lapse of time between acquiring the characteristic and having offspring.

Explanations of this tended to turn on ideas about development of the brain (what the brain "knew" about the form of the organism) than genes as controlling agents. There were some differences in responses for humans and dogs. For instance, the children felt it more likely that a human baby would be affected if both parents had lost a finger than if only the father had this characteristic - but this effect did not appear in the answers given for dogs.

On probabilities of inheriting particular traits, there was a tendency to ascribe more influence (on e.g. coat colour) to the mother: "they take after the colour of the mother because she takes care of them". When it came to height, there was a range of responses. Some saw human children's height being mostly determined by the same-sex parent; some by the male parent, because it is a male contribution (as opposed to hair, eye colour, or shape of nose); some, mostly older, had more complex ideas involving both a probabilistic element (it depends who you take after) and environmental influences on height.

In analysing all the explanations, Kargbo et al offer a fourfold classification. Environmental explanations; somatic explanations (some part of the body determines the offspring's characteristics - nerves, brain, blood etc.); naturalistic explanations - girls are like their mums; genetic explanations. Only four of the 32, all aged ten or over, gave responses like this.

They conclude that there is no evidence for an age-related developmental trend in concepts related to the inheritance of a deformity, but that there may be such a trend in development of less rigid, probabilistic thinking.

Two years later Longden published a short paper which describes a study trying to tease out specific learning difficulties with genetics encountered by a small group (10) of A-level biology students who were otherwise judged capable and well-motivated (Longden, 1982). It is thus concerned with higher level ideas than the above, and goes further into technicalities of terminology and representation. The conclusions are directed toward specific features of classroom/laboratory presentation of genetics, and especially meiosis, which is apparently a source of great confusion. So far as the data is relevant to general public understanding of genetics, one interesting finding is the problem the interviewees had with the various levels of inclusiveness which are implied in the technical language of genetics (e.g. allele - gene - chromosome - genome - cell). The standard symbolic representations of crossing over (which come in several variants) were also found very hard to manipulate. The first point also comes over strongly in the discussions with school teachers reported by Ogborn's group (see below).

Clough and Wood-Robinson reported on a British-based study which follows on from Kargbo, and extends the above findings in ways broadly consistent with the earlier study (Clough and Wood-Robinson, 1985). It was part of a wider exploration of understanding of biological and physical topics. 84 students aged 12-16 from three city comprehensive schools answered a variety of questions about inheritance. Again they found a minority who believed in inheritance of acquired characteristics in the first generation (around 20 per cent believed mice with docked tails would have tailless offspring). The majority who believed this wouldn't happen thought it was simply because it "wasn't natural". Only a small number explained it in terms of invariant genes.

Almost half believed that while acquired characteristics are not inherited immediately, they can be inherited after several generations (e.g. as athletes train their descendants).

Responses to questions probing understanding of intraspecific variation showed "very few students (7 per cent) indicated a good understanding of the nature of gene function, though about a third of the students interviewed suggested that a genetic entity (of unspecified nature) was passed on at fertilisation to determine phenotypic features. This latter group did not demonstrate any detailed knowledge of the mechanism of gene action, but simply of the basic idea that characteristics are determined by a particulate genetic entity, which carries information translatable by the cell".

Non-standard ideas which cropped up included:

- belief in transfer of likenesses during development of the embryo;

- "... genes are cells which are passed on from the mother to the baby when the baby's inside ... its when the baby is developing".

- belief that parental contributions to genetic make-up are unequal - for example expressed in the idea that identical twins resulted from one egg and two sperm; sometimes in the idea that one characteristic is due to one parent, one to another (same sex inheritance being stronger also appeared) c.f. Kargbo.

- An alternative explanation for identical twins was the idea that all eggs or sperm released at the same time bear identical characteristics; "perhaps the whole lot of sperm that swims towards the egg all carry the same ingredients for a person"

- There was also widespread misunderstanding of the ideas of dominance and recessiveness, dominance being equated with expression.

As with the earlier study, the numbers are too small to give any real indication of prevalence of such alternative conceptions.

An alternative approach to questionnaires for probing understanding is to monitor group discussions as people try to make sense of how heredity works. Ogborn and colleagues studied the explanatory models constructed by groups of British primary teachers invited to discuss a range of scientific subjects after exposure to some preliminary "popular" material. They report a number of particular problems with genetics (Ogborn, 1992).

One problem was understanding the relations between entities of different level or size - bases, DNA, genes, chromosomes, cells - what is part of what? This emphasises the widespread problem in public understanding of science in visualising phenomena which are outside the normal mid-range of human sensory experience, and where our intuitions offer no guide.

In this case, there was consensus that bases were at the bottom of the hierarchy, that genes are something very small, and that they encode information. But, "it was when the discussions tried to place DNA, genes and chromosomes into the picture that the problems arose. A major sticking point for virtually all the groups was whether genes are made of DNA or DNA is made of genes" (emphasis added).

Related to this, these groups were often hazy about what genes might be like, how their structure might relate to their function and how many there might be in any one cell. As the last doubt implies, there was confusion about whether genes are the same in all cells, when cells differ so widely. Finally, they could make little sense of how genes do what they do : "the teachers had no problem with the idea that genes in some way make you the way you are. They are the information that determines the characteristics of living organisms. The groups were also conversant with the notion that genes are passed down from one generation to the next. Where the teachers could not move forward in their discussions was when they were considering how genes make you the way you are; 'genes carry information... that's about all we know'".

This suggests that some version of the ideas of classical genetics has become much more widespread in popular understanding than the more recent molecular genetic ideas. Indeed these authors suggest that the classical ideas have come to seem so near-intuitive, or commonsensical that they block curiosity about the next level:

"The groups had very little access to information that would help them discuss the processes and mechanisms involved in genetic determinism. Indeed, it was often the case that the teachers did not even see the need to talk about genetics at any level beyond 'genes make you the way you are'. It was almost a silly question to ask how genes do this. 'They just do'. It was as if the notion that genes make you the way you are is so ingrained in everyday thought that asking 'how?' was no longer seen as a significant question necessitating a consideration of scientific ideas in order to arrive at an answer. It was self-evident that genes make you the way you are and no further consideration of the issue is required".

In the more general discussion, a number of further questions emerged which many of these groups could not answer to their own satisfaction:

- Why aren't engineered genes rejected?

- Do animal and plant genes work in the same way?

- If all the genes are always present how does a cell know what to become/make?

- Are cancers inherited?

- How do genes give you blue eyes?

Again, difficulties of this sort reinforce the impression that while the idea that genetic information is encoded in DNA is a good start, it often leaves people unable to build useful mental models of how the information is used.

Finally, a further recent study in the same area by Ogborn and colleagues has focused on the kinds of metaphorical work which can be codified in conversations about genetics (Ogborn et al, 1993). This was a small-scale study, again using interviews with primary school teachers, who were asked to read a basic text about DNA and then consider a series of questions:

- How can genetic traits last for many generations?

- How might genetic fingerprinting be possible?

- How do the different parts of the body get to be different?

- How is genetic engineering possible?

From the responses, these authors suggest that there was a basic model of genetic inheritance which most of the teachers used, involving an association between a discrete, particulate gene and a discrete feature of the organism - like eye colour.

The details were typically vague: "it was very common for the teachers to be sure that genes must be some kind of particle located somewhere, able to move and act, whilst remaining puzzled or unsure about what kind of object they are, where they are located and how they might act. But that they would be somewhere, and be some kind of object, was usually tacitly assumed."

The detailed analysis of further metaphorical work in these discussions relates closely to the puzzles displayed in the earlier study. The subjects grappled with a series of conceptual problems, defined by the authors as:

The identification problem - is a gene inside or outside the DNA?

The existence problem - where does DNA come from?

The localisability problem - is a gene in one place, or is it everywhere?

The combination problem - does genetic material join by combining or mixing?

The activity problem? - some situations seem to require genes to act on other things; some to be dormant.

The differentiation problem.

Each of these is discussed in detail in the paper. This work, although based on only a few interviews (14) begins to get deeper into how people work toward their understandings of genetics (or, the authors argue, anything else) than previous studies.

d) Media studies and popular culture.

I am not going to discuss this area in detail here. The area of media representations of genetics is ripe for empirical work, some of which is under way. Dorothy Nelkin and Susan Lindee will shortly publish a book in the US about their work on ideas about genes in public discourse, for example. But it is important to emphasise that ideas about heredity and genetics reach people through many channels, and that both surveys of understanding and studies of the success or otherwise of formal education are the poorer if they neglect these influences. A full discussion would require a separate paper, so I will confine myself here to a few general observations and some specific examples.

The first general observation is that the new genetics is a working through of the Baconian project in biology, and that prospect has a rich history of evoking ambivalent responses, most often responses which are shaped by the Frankenstein myth (Turney, 1994c). Studies of mass media coverage of genetics show that the Frankenstein story is still a dominant framing of accounts of modern research (Durant et al, in press).

The many stories in this vein - whether in news reports or as fiction, film or comic books, can be taken to have their main effects on expectations and attitudes. The influence of popular culture on understanding is of course harder to tease out. There are well documented suggestions that the way genetics is reported, often under the influence of scientists' rhetoric, promotes ideas of genetic determinism at the expense of more nuanced views of the interaction of genotype and phenotype. This is, of course, an old debate, but Nelkin has suggested that the promoters of the human genome programme have recently amplified this tendency (Nelkin, 1994).

In film and fiction (or science fiction), there is much material to examine. Some recent authors are explicitly writing to provoke discussion of the new biology (Stableford, 1991). Some have reframed earlier stories with the same intent ( Sargent, 1976). And there is of course a vast amount of pulp fiction, and its video equivalent, which deals with monsters, clones, cyborgs, chimerae and hybrids of all kinds.

One immediate impression is that all this fictional work helps to reproduce older ideas about inheritance - the ideas implicitly underlying many such tales appear to be pre-Mendelian, if not mediaeval. No complete history of such stories exists, so far as I know, although available reference works confirm this impression (Brosnan, 1991, Nichols and Clute, 1994). I will confine myself to just a couple of examples which reinforce it.

Consider The Fly, a classic horror film made in 1958. In the original, the scientist at the centre of the action is accidentally transmuted when a fly intrudes into his experimental matter transmitter. The result, a man with a fly's head, though still capable of human emotions and reason, and a fly with a miniature man's head. So far, so illogical.

More interesting for my purpose is the remake, with famously repugnant special effects, by David Cronenberg in 1986. This removes some of the obvious absurdities of the original by dispensing with the miniature fly/man. And it gives a new, up to date warrant, for the gradual transformation of the scientist, Brundle, into a fly. When he interrogates the computer system controlling matter transfer about the cause of his new state, the words "integration at the molecular genetic level" appear on the screen. This seems a clear example of blending inheritance brought into the age of molecular biology.

Less spectacularly, consider an item from the US Supermarket tabloid The Weekly World News for April 26, 1994. Headed:

"Farmer breeds cow with pig", it describes a hybrid animal produced by artificial insemination, and with meat which "tastes like a real bacon burger". Again, blending inheritance is the underlying notion at work here.

Obviously no-one is going to take either The Fly or the Weekly World News seriously as accounts of inheritance. But it is equally obvious that the continued visibility of these ideas in such contexts makes them salient for some people when they are trying to understand real questions of human inheritance.

It would be useful to have a more comprehensive study of fictions of heredity - either historical or contemporary - along these lines. Until this is done, these few examples may serve to highlight the importance of popular culture in this area.

CONCLUSION

Taken together, the four areas of inquiry reviewed above can tell us quite a lot about the public understanding of genetics - this effort to pull together a somewhat scattered literature certainly suggests that a good deal of useful work has been done. Some of these research trails could and should be followed further. But there is one feature of all this work which deserves a corrective. Little, if any, attention is paid in these studies to why people might want to understand genetics, and what exactly they might wish to know.

Work like this needs to be complemented by studies which take more seriously the argument I outlined in the opening section of this paper: that it is necessary to recognise the importance of the context in which knowledge is acquired, and to pay heed to the problems and agendas for concern of those seeking knowledge, rather than try to implement a "top-down" prescription of what the relevant knowledge is.

Two studies which do take this point of view seriously also have in common that they call into question the importance of knowledge of genetics in managing what are, ostensibly, genetic conditions. In the practical, day-to-day, decisions taken by parents of children with Down's syndrome (Layton et al, 1993), or patients with familial hypercholesterolaemia and their relatives (Lambert and Rose, in press), genetics, or indeed science as a whole, may be of only marginal relevance.

Among the hypercholesterolaemics, Lambert and Rose found that:

"very few patients are aware of, or display interest in, the details of the metabolic processes that are implicated in their condition, or in the exact nature of the genetic defect that causes their cholesterol levels to be raised. Instead, they operate on a 'good enough' level of knowledge for their purposes. Thus most, and especially those with children, have views on the transmissibility of this genetic disorder over generations, and almost all are highly conversant with nutritional information that bears on how dietary modification for the disorder may be dealt with in everyday life".

A similar, and in some ways more trying, negotiation with a "scientific" account of a particular condition is described in Layton's study of parents of children with Down's syndrome. As he reports, "what the parents were seeking was knowledge which articulated with their perceptions of what needed to be done, short-term, immediately, within their own particular setting". In this context, information about chromosomes was most commonly seen as "irrelevant and of no practical use to new parents".

These two examples come from studies in very particular contexts of use, of course, and the contexts in which genetic information may be useful in future will be much wider than this - from policy-debate to health insurance and legal evidence. But the fundamental point still holds that we have little notion of what kinds of genetic knowledge people will find it useful to develop.

This is an area which could perhaps be explored through qualitative research, posing particular questions to groups of lay discussants, or putting particular scenarios before them, and exploring what kinds of knowledge they consider relevant to evaluating the issues which arise.

Research like this could provide a way of focusing further work which is more along the lines which have already been established, as well as helping to guide the creation of educational materials. The open question is not so much what do people know about genetics, but what do they want to know?

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