The Blackwell Companion to Sociology (52 page)

this story that captures the attention of social analysts of science, and that is the putativèèthnic purity'' of the database. The Science magazine reporter who

covered the story had this to say about why Iceland would be a potential genetic gold mine: ``Thanks to its isolated position and several bottlenecks that wiped

out large parts of this population, the island has a remarkably homogenic gene

pool, making it relatively easy to track down disease-causing mutations that

might form the basis for new tests and therapies'' (Enserink, 1998, p. 891).

The degree to which this is true, of course, is an empirical question that awaits an answer with potentially volatile economic and political consequences. The

major point to be made here is that this development has generated a consider-

able amount of interest from a number of sociologists and anthropologists of

science. They have been joined by bio-ethicists and political scientists in a Great Trek northward to monitor and study these developments. While the molecular

geneticists are concerned primarily with tracking down what they regard as

``disease genes,'' the social analysts of science are focusing on the wider set of issues that can have a large impact on a full panoply of social relations ± not only in Iceland, but as a harbinger of things to come, globally. So it is the case that work in the laboratory of the biological scientists has ``taken off' and refocused the attention of the sociology of science.

Katz Rothman (1998) has pointed out how communication (or lack of it) of

the technical intricacies of the molecular genetics revolution is often silencing and disempowering ± intimidating to those not able to follow closely

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developments at the vanguard laboratories of the field. Yet these technologies are driven by profoundly social, political, and economic questions and concerns. It is therefore both useful and necessary to demystify the complexity, and to be able

to cut to the core of basic elements of the scientific work. Then we will be better able to understand what the Iceland adventure is all about, and why it has such a powerful grip on the imagination. We will then see why issues of race and

ethnicity, health and medicine, and crime and violence will all be impacted in

new ways.

A Short but Necessary Primer on SNiPs

Although the work is named The Human Genome Project (the mapping and

sequencing of all human genes), no one particular DNA sequence constitutes the

human genome. Rather, each person (with the exception of monozygotic, or

identical, twins) has her or his own unique human genome, or set of complete

genes.

DNA is made up of four chemical components, called nucleotides. These are

strung together in a chain, much like beads on a necklace. The four different

nucleotides are represented as ``G'' (guanine), `À' (adenine), ``T'' (thymine), and

``C'' (cytosine), and a DNA sequence could look like GCGCATTAGCTACGG.

Each molecule is in the form of a disc, and is called à`base.'' Rungs of the now famous DNA ladder are constructed when two of these nucleotides are connected in a spiral and form what is called à`base pair.'' The DNA of humans is

made up of approximately three billion nucleotides that are packaged into 23

nuclear chromosomes and one mitochondrial chromosome. Approximately 10

percent of these base pairs are called genes. Each of these codes for the production of a particular protein.

If someone is missing à`correct'' sequence of DNA in one of those segments,

that particular protein will not be made. That could prove vital, fatal, or painful.

For example, hemophilia is a condition where blood does not clot properly.

Those with hemophilia have stretches of the DNA with `èrrors'' that inhibit the

protein that would instruct blood to clot properly. Quotation marks have been

placed around ``correct'' and `èrrors'' for an important reason. While there may be a relatively high consensus about what constitutes a debilitating or fatal

disease condition (e.g. Tay-Sachs is a neurological disease that is fatal by age four), that consensus falls away for many other conditions. Setting a single

standard of ``normality'' is always about the power and position to do so. In

the United States and Europe, many communities of deaf persons resist the idea

of being ``corrected.'' This raises the question of who will set the standard of thè`normal'' human genome.

Maps of the genome allow researchers to locate a piece of DNA somewhere in

the genome, but that map will not indicate the precise arrangement of the

nucleotides in that piece of DNA. The precise arrangement, or linear order, of

nucleotides is called the DNA sequence. The DNA sequence is important

because different sequences encode different information. One of the main

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reasons for studying DNA is because it encodes information that specifies how

cells should make biologically useful molecules, such as proteins.

If we compare the complete DNA sequence of any two people we will find a

difference approximately one time in every thousand nucleotides. The simplest

kind of difference is when one nucleotide differs between the two people; for

instance, when one person has a G at a certain position in the sequence and

another person has a T there. In some cases, such differences will cause a slightly different protein to be made. In other cases, these differences have no known

impact on which protein is made or on any other biological functions.

Places where people's genomes differ by one nucleotide are called ``single

nucleotide polymorphisms,'' commonly shortened to SNiPs. The search for

SNiPs is now in full bloom because these SNiPs can be used as ``markers'' on

chromosomes. These markers can be used to make genetic maps which may

allow us to locate genes of interest, such as genes involved in diseases. But they can also be used to identify and mark both individuals and groups of individuals, a technological capacity that will prove to be of extraordinary significance and consequence to social studies of science.

SNiPS on Chips

Many things that molecular geneticists want to study, including many (if not

most) human diseases, are caused by a complex interaction between things in the

person's environment and the person's biology, including many different genes.

In the past decade, media accounts of ``the gene for'' this or that disease,

condition, attribute, or behavior have become common, sometimes weekly,

reports. This has led many lay persons to believe that a single gene is the cause of a host of diseases, attributes, and conditions. Yet it is only in rare cases that a single gene has a very strong, identifiable effect on whether or not a person

contracts or develops a disease. Such cases are generally called ``single gene

disorders.''

In most cases, when genes play a role in the development of a disease, such as a particular kind of heart disease, the role of any single gene will be very small.

To study the genetics of complex conditions such as heart disease, methods must

be devised for finding a constellation of genetic differences between people

that correlate with that disease. One method for examining many different

pieces of DNA all at once, and for detecting more than one genetic difference

in a single experiment, is to put many different genes or parts of genes on a

computer chip.

DNA chips are useful for doing the equivalent of 100 or even 1,000 experi-

ments all at one time, in one simple procedure. The chip with dimensions less

than one square centimeter may have 1,000 or 10,000 different sectors. The

technology is now available to attach DNA of a slightly different sequence to

each sector. For instance, suppose that a group of researchers had found 2,000

different SNiPs; that is, 2,000 identifiable places in the genome where people's DNA sequences could differ by one nucleotide. Then, someone could make a

DNA chip that would have all the possible SNiPs (at least 4,000, but it could be 218

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more because each SNP will have between two and four possibilities), each in its own separate and identifiable place on the chip. Then, if my DNA were exposed

to the chip (actually, DNA or RNA are hybridized to the chips), one experiment

could determine which SNiP I had at all 2,000 different places in the genome. We could make à`SNiP profile'' for me. If we did this for 5,000 people, 2,500 of

whom had a certain kind of heart disease and 2,500 of whom did not, then we

might be able to find five to ten SNiPs that were correlated with a high likelihood of developing heart disease. That is the core of the methodological strategy of

SNiPs on chips.

SNiPs, Human Diversity, and Social Groupings

Approximately 85 percent of human genetic diversity can be found in any

population, even a very small, village-sized population (Cavalli-Sforza, in

Smith and Sapp, 1997, p. 55). For instance, if we were looking at SNiPs, we

would find that most are in all populations throughout the world. However,

there will be some SNiPs that are found in some people from Finland but

probably not in people of Native American descent. This does not mean that a

certain sequence is found in all people from Finland, or that it is never found in people who are not from Finland.

There are social implications of creating SNiP profiles if these can be used to

suggest increasing likelihood of a person's ancestry and appearance, for example.

As we shall see, forensic studies that attempt to provide the criminal justice

system with strong leads to probable suspects are now being developed. Because

phenotypical stereotypes of ``race'' have played a large role in such identification, we must first turn to the literature that sets the stage for the re-emergence of

``race'' in molecular biological clothing.

Context

Context and Content

Content for Feedback Loops:

Loops: Setting the

Empirical Problem

By the mid-1970s, it had become abundantly clear that there is more genetic

variation within the most current common socially used categories of race than

between these categories (Polednak, 1989; Bittles and Roberts, 1992; Chapman,

1993; Shipman, 1994). The consensus is a recent development. For example, in

the early part of the twentieth century, scientists in several countries tried to link up a study of the major blood groups in the ABO system to racial and ethnic

groups (see Schneider, 1996). They had learned that blood type B was more

common in certain ethnic and racial groups ± which some believed to be more

inclined to criminality and mental illness (Gundel, 1926; Schusterov, 1927).

They kept running up against a brick wall, because there was nothing in the

ABO system that could predict behavior. While that strategy ended a full half-

century ago, there is a contemporary arena in which hematology, the study of

blood, has had to resuscitate a concern with ``race.''

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In the United States, there has been an increasing awareness developed over

the past two decades of the problem that blood from Americans of European

ancestry (read mainly white) tends to contain a greater number of antigens than

blood from Americans of African or Asian ancestry (Vichinsky et al., 1990). This means that there is a greater chance for hemolytic reactions for blacks and

Asians receiving blood from whites, but a lower risk for whites receiving blood

from Asians or blacks. Here we come to a fascinating intersection between the

biological and social sciences. In the United States, not only do whites comprise approximately 80 percent of the population, but proportionally fewer blacks

and Asian Americans donate blood than do whites. This social fact has some

biological consequences, which in turn have some social consequences.

Approximately 400 red blood cell group antigens have been identified. The

antigens have been classed into a number of fairly well defined systems: the most well known are the ABO and Rh systems, but there are other systems, such as P,

Lewis, MN, and Kell (standard hematology texts note ten systems, including

ABO and Rh). The clinical significance of blood groups is that in the case of a

blood transfusion, individuals who lack a particular blood group antigen may

produce antibodies reacting with that antigen in the transfused blood. This

immune response to alloantigens (non-self antigens) may produce hemolytic

reactions, the most serious being complete hemolysis (destruction of all red

blood cells), which can be life threatening. Once generated, the capacity to

respond to a particular antigen is more or less permanent, because the immune

system generates ``memory cells'' which can be activated by future exposures to

the antigen. For those who have chronic conditions, which require routine blood

transfusion, this aspect of the immune response is critical, because it increases the likelihood of future transfusion incompatibility. The clinical goal is to minimize immune responses to antigens in transfused blood, in part because a crisis (such as trauma surgery) may require transfusion of whatever blood is available, regardless of its antigen composition.

Most blood banks only test for ABO and Rh ± the most common systems.

Testing for the other systems is considered inefficient and will increase the cost of blood. It is essential to minimize the antibodies against blood group antigens for everyone. However, the way in which blood typing is done puts members of