Race in the Genes


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Race in the Genes

  1. 1. Citation: "Race in the Genes." Today's Science On File June 2003. Today's Science @ FACTS.com. Facts On File News Services. 12 Dec. 2006 <http://www.2facts.com>. Race in the Genes Issue: June 2003 Keywords: race, DNA, mutation, Human Genome Project Aris Messinis/AFP Racism protestors argue that racial differences are purely cosmetic. In fact, according to recent research, one's skin color may have little to no correlation with one's genetic heritage. All the more reason to ignore skin color when it comes to politics. People around the world look different, and society tends to classify these physical differences as "races," which implies that there are significant genetic differences. The truth is that humans around the world are strikingly similar genetically, and that the differences that do exist are more related to geography than to physical characteristics. A study published in the journal Science in December 2002 indicates that of the dozens of populations in the world, there are five basic groups that correspond to the planet's major geographic regions. By examining scans of the entire human genome , or genetic code, the researchers found patterns corresponding to different geographic regions where early humans settled. Though sociologists and anthropologists , scientists who study the origins and structures of human society and culture, maintain that race is more a cultural construction than a biological one, the study essentially confirms the popular conception of race, according to lead author Marcus Feldman of Stanford University. The five races, which divide roughly along continental lines, are Africans, Europeans and Middle Easterners, East Asians, Melanesians (South Pacific islanders), and the American Indian populations. "What the study says is that if you look at enough markers you can identify the geographic region a person comes from," said Kenneth Kidd, another of the researchers, from Yale University. What has given researchers access to the human genetic code is the Human Genome Project , which began in 1990 as a coordinated effort by the U.S. Department of Energy and the National Institutes of Health. It was originally thought that the project would not be completed until 2005, but rapid technological advances make it likely that it will be completed sometime this year. [See 2003 Human Genome Fully Sequenced] The stated goals of the project are to identify all the approximately 30,000 genes in human DNA ; determine the sequences of the three billion chemical base pairs that make up human DNA; store this information in databases; improve tools for data analysis; transfer related
  2. 2. technologies to the private sector; and address the ethical, legal and social issues (ELSI) that may arise from the project. A genome is an organism 's entire DNA sequence, which contains instructions for all the biological activities of that organism. DNA consists of 4 chemical bases . The combinations are repeated over and over, in a variety of patterns. Genomes vary in length from that of a bacterium , with about 600,000 DNA base pairs, to those of humans and mice, with about three billion pairs. Every human cell except for the red blood cells contains a copy of the complete genome. A gene is a DNA sequence that encodes a protein . Proteins perform a multitude of specific functions, ranging from stimulating growth to determining hair color. The estimated 30,000 to 40,000 genes on the human genome constitute only about 2% of the entire genome. The rest of the DNA consists of non-coding regions whose functions are unclear. The process of evolution occurs when genes mutate, and one or more of the bases in a DNA sequence changes. If the change is beneficial, and it helps the individual organism survive, it is passed on to subsequent generations as they evolve to become different organisms. If a harmful mutation occurs on a gene, the organism will likely die without passing on the mutation to future generations. For instance, there are genes that can be found in insects, humans, and everything in between. The fact that these genes are identical in all living organisms shows that they are absolutely essential to life, and go back to the dawn of evolution. Any time these key genes mutated, the organism died and the mutation was not passed on to a new generation. This means that the more widespread a DNA sequence is among different organisms, the older the gene. Humans share only 31% of genes with yeast, but 98% with chimpanzees, showing that it took far fewer mutations for chimpanzees to evolve into humans than for single-celled organisms to evolve into humans. Gerard Julien/AFP Geneticists have determined that there are five main geographical populations from which most people in the world today originated. The vast majority of genetic differences are irrelevant, but the few differences between groups may allow doctors to better tailor health care since certain genetic heritages also bring health tendencies. When mutations do occur, they can appear at any point along the entire length of the genome. There are mutations in genes that change the organism because they change the code that calls for a specific protein (the cell's building block). But there are also mutations in the nonfunctional sections of DNA. These regions of nonfunctional DNA near a given gene act as "markers" of that gene. When researchers try to determine the age of a gene, they prefer to study the rate of mutation in the marker regions rather than in the gene itself, because mutations within the gene can change the organism's
  3. 3. chances of survival. For example, if a harmful mutation occurs in an important gene, the organism will die. Scientists will never know that the harmful mutation happened and will only count the beneficial mutations that survived, thus underestimating the age of the gene. However, mutations within non- coding DNA are not as subject to selective pressure. Hence, they provide a more reliable picture of a gene's age. The team from Stanford conducted the study on human populations for the Human Genome Diversity Project. They examined 377 markers on the genomes of 1,056 individuals from 52 populations worldwide. The population included Bantu and Mbuti Pygmis from Africa; Basques and Italians from Europe; Bedouins and Palestinians from the Middle East, Sindhis and Kabashes from Central and Southeastern Asia; Mongolians and Japanese from East Asia; Melanesians and Papuans from Oceania; and Colombians and Mayans from the Americas. The two major populations missing from the study were the Australian aborigines and Indians (from India), two groups that are unwilling to donate their blood for genetic analysis. The team discovered that 95% of the genetic variances among all people—the small number of differences between your 30,000 to 40,000 genes and those of your neighbor—are irrelevant, and do not allow scientists to distinguish between populations. For example, two Spaniards can be as genetically varied as two people whose genetic lines originate on opposite sides of the world—say in Asia and America. You would still not be able to tell which pair was which by examining most of these differences. A mere 5% of genetic variability can be linked to geographic factors. Humans are overwhelmingly genetically similar, no matter where they come from or what they look like. The 52 populations all fit approximately into one of the five major geographical populations, though most of the geographic areas included some mixture of groups. For instance some populations from the Middle East are a mix of African and European populations and some populations from Central/South Asia are a mix of Europeans and East Asians. The ability to classify people genetically can bolster biomedical research and treatment because different health problems are concentrated in different populations. By taking genetics into account, doctors can more readily diagnose certain diseases. For instance, the African population has a high incidence of sickle cell anemia , a disease that hampers the delivery of oxygen to cells. Meanwhile 7.5% of Swedes have hemochromatosis, a disease that disrupts the metabolism of iron. When treating an individual from a particular population group, a physician can know immediately whether the patient is likely to have certain conditions. Also, the doctor may be able to determine what drugs to prescribe, based on that genetic population's response to certain medications. The researchers found that "self-reported population ancestry"—that is, an individual's belief about his or her genetic origin—"likely provides a suitable proxy [substitute] for genetic ancestry" and also tends to fall into one of the 5 populations. They found little variation between people's genetics and their self-assigned race, except in some Middle Eastern groups. However, overall, people who identify themselves as Melanesians, for instance, will most likely have genetic characteristics of other Melanesians. So in order to obtain information to diagnose or treat disease, doctors need only ask a person for his or her race or continent of origin, which "is less expensive and less intrusive" than analyzing DNA, according to Feldman. This new information also makes it easier to determine when and where historic migrations took place. Humans first evolved in Africa and likely began to disperse 50,000 years ago. As they moved across the planet, populations experienced unique genetic mutations, some of which resulted in physical changes such as alterations in skin color and body shape. Many of these mutations were selected for by environmental influences such as sunlight and terrain. By looking at the genomes of people from different populations, researchers are able to tell whether a mutation happened before or after the population dispersed.
  4. 4. But once race enters into a scientific study, there is always the potential for abuse. The debate about whether race is cultural or biological is a long-standing one. Past scientific research involving race has been used to promote false ideas. Genocide and other atrocities such as the Holocaust and American slavery have occurred when people insisted that there were significant genetic differences between race and ethnicity. Many researchers shy away from the term "race"; this study referred to "population structure" and "self-reported population Genetic analyses show that skin color ancestry." In an interview with the New York Times, Feldman has little to do with genetic heritage. said, "We need to get a team of ethicists and anthropologists and some physicians together to address what the consequences of the next phase of genetic analysis is going to be." According to the American Sociological Association (ASA), "Race is a social construct." It warns that this study is in "danger of contributing to the popular conception of race as biological." Even so, Troy Duster, a professor of sociology at New York University and chairman of the committee that issued the statement, cautions that sociologists do not have the expertise to make judgments about genetics. Neil Risch, a population geneticist from Stanford, argued recently that race is actually a legitimate area for medical research. Feldman claims that his study backs up Risch's argument, because it reflects the differences that developed after the first humans migrated away from Africa. Despite findings that there are five major genetically distinct races, and that most people correctly identify themselves as a member of the race indicated by their genes, physical characteristics do not necessarily correspond with these five population groups, according to a Brazilian study. The study, conducted by scientists at the University of Minas Gerais in Brazil and the University of Porto in Portugal, appeared in the January 7, 2003 issue of the Proceedings of the National Academy of Sciences. The study was conducted in Portugal, on the island of Sao Tome (a former Portuguese colony off the African coast), and in Brazil. By looking at ten gene variations between 20 men in Portugal and 20 in Sao Tome, researchers found that they could tell the men apart based on those genetic differences. But surprisingly, the ten genes had nothing to do with physical characteristics like skin or hair color, the traditional markers of race. Brazil's population is also a mix, of Amerindians, Europeans, and Africans who have intermarried over centuries. Even so, many Brazilians are considered "white" and many are considered "black." The researchers tested 173 Brazilians who were divided up into groups of "white," "black" or "intermediate," and another group of 200 "white" men. Their DNA showed that even white people had 33% Amerindian genes and 28% African genes. The researchers wrote, "It is interesting to note that the group of individuals classified as blacks had a very high proportion of non-African ancestry (48%)." This study shows that equating color with geographic ancestry is misleading, though it is how most people initially make racial assumptions. There is a difference between white, Caucasian and European, even though most people use them interchangeably. Likewise, there is a difference between people who are considered black in different parts of the world and those who are African. They don't all mean the same thing. Though Sergio Pena, one of the researchers who conducted the study, told the BBC News "There is wide agreement among anthropologists and human geneticists that, from a biological standpoint, human races do not exist," it looks as though the more we learn about human genetics, the more debatable that assumption becomes.