Scientists have traditionally viewed genetic research as the key to understanding the human body. Research studies have been funded to search for genetic disorders that can cause disease. Some diseases for which a genetic defect is known include muscular dystrophy, cystic fibrosis, sickle cell anemia, and Huntington's Disease. In 1970, however, the National Institutes of Health (NIH) used genetic testing as a tool to explain why some people commit crime.
Genes are the Basic Unit of Heredity
The fundamental unit of heredity is a gene. A gene is made up of DNA, which is the basic building block of life. There are two types of genes in the human body, of which the most important is the gene responsible for making proteins. According to the Human Genome Project, the human body contains anywhere from 20,000 to 25,000 genes.
Organisms pass along genes from one generation to the next. Genes contain information that allows cells to develop and organisms to grow. A trait is any characteristic controlled by a gene. Physical traits such as hair color and blood type are inherited from genes, along with personality traits such as intelligence or musical talent.
Chromosomes are the Key to Genetic Research
All species have different numbers of chromosomes. A chromosome is a threadlike structure consisting of bundles of DNA wrapped around small proteins called histones. Each chromosome is made up of several hundred to several thousand genes.
Human beings have 46 chromosomes: 2 (X, Y) sex chromosomes and 22 pairs of autosomes. Genetic research usually begins when scientists organize chromosomes in pairs and by size (from largest to smallest). The resulting profile is called a karyotype, which is used to detect abnormalities.
Females have two X chromosomes, while males have an X chromosome and a Y chromosome. The normal female karyotype is 46-XX, while that of a normal male is 46-XY.
A Chromosomal Anomaly Leads to XYY Syndrome
In 1961, Sandberg et al. discovered a chromosomal anomaly in which a random error in cell division caused human males to receive one extra Y chromosome. Instead of 46 chromosomes, males with this condition have 47 chromosomes. The extra copy of a Y chromosome produces a 47-XYY karyotype.
Approximately 0.1% of all males have an extra Y chromosome, which contributes to their genetic makeup. Males with this karyotype are said to have XYY syndrome.
Although males with XYY syndrome are otherwise normal, some developmental delays and characteristics have been associated with the extra Y chromosome, including:
- Tall stature
- Lean and muscular build
- Acne
- Learning difficulties
- Bad temper.
When the 47-XYY karyotype was discovered, it was suggested that males born with this condition would be prone to aggressiveness, and thus more likely to possess abnormal personality disorders such as criminal behavior.
Is Criminal Behavior Caused by an Extra Y Chromosome?
In 1968, Neilsen et al. reported a study conducted on criminally insane Danish prisoners who had committed arson. Of the 155 prisoners who underwent chromosomal analysis, 2 (1.3%) had the 47-XYY karyotype. As this percentage was 26 to 65 times higher than the percentage of males in the general population with the same extra chromosome, the researchers concluded that men who committed arson also were more likely to have the abnormal karyotype.
According to Harris (2005), a similar study was conducted in correctional institutions that housed psychiatric patients. The researchers claimed that those prisons had anywhere from 3 to 20 times more males with an extra Y chromosome than in the general population.
Of course, both research studies were based on faulty logic. The researchers did not take a cross-section of the general population and look for the 47-XYY karyotype. Instead, they started with prisoners and then looked for what qualities made them different from the general population. Nevertheless, their conclusions attracted the attention of the U.S. government.
The NIH Targets African American Males
Throughout the 1960s, crime increased in cities throughout the United States. Despite societal pressures caused by the Vietnam War and the assassination of political leaders such as Martin Luther King, Jr., the government still wondered why violence was so high in urban areas.
In 1970, the NIH funded a study through Johns Hopkins University in which 7,000 African American teenagers were recruited as subjects. In order to obtain informed consent, the investigators told the parents that blood samples would be collected in order to test for sickle cell anemia, which was then a concern among the African American population.
In reality, however, the researchers were looking for XYY syndrome and the extra Y chromosome that was thought to be a genetic link for crime. News of the testing provoked outrage in the African American community.
In the end, none of the African American teenagers had the 47-XYY karyotype. The NIH quietly ended the study, but it would not be the last time that one segment of the population was racially targeted for political reasons.
References
Harris V. 2005. 22q11 deletion syndrome and forensic research: can we go there? J Am Acad Psychiatry Law. 33:106–111.
Neilsen J, Tsuboi T, Stürup G, Romano D. 1968. XYY chromosomal constitution in criminal psychopaths. Lancet. 7(7567):576.
Sandberg AA, Koepf GF, Ishihara T, Hauschka TS. 1961 (August 26). An XYY human male. Lancet. 2(7200): 488–489.
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