I have recently read a little bit on genetics and behavior. Here I will share some of the new things I have found out.
1. Genetic drift. This I have actually known for quite some time, but natural selection and mutation are not the only ways in which evolution occurs. There is also sexual selection and a phenomenon called genetic drift. Because individuals have two copies of each gene, and pass one on their offspring randomly, chance variations of inheritance can make one genetic variant more common than another, even without any occurence of natural selection. This is more likely to occur in initially small populations. Therefore, it is important to be aware of that not every trait in humans have had an evolutionary advantage but just be a random occurence. 2. Gattaca. The name of the movie Gattaca, about a dystopian eugenics society, derives from the four bases of the DNA molecule; A, T, G and C. 3. On the genetic similarity between humans and other mammals. Rarely does evolution drop genes or create entirely new ones, and is for this reason that mammals have comparable gene counts. However, as evolution progresses, some genes can start working together or acquire slight mutations to perform new functions. It is also believed that the so called "junk DNA", DNA that does not code for any proteins, actually do have functions. It is for this reason that humans and other apes may be very similar in regards to their genome, but very different in abilities. 4. Genes and behavior. There are many example of the relationship between genes and behavior. People with defective FOXP2 genes suffer from language impairment, defects in the APOE gene is related to Alzheimers' disease, the IGF2R gene is related to intelligence, and the ASPM gene (a gene related to brain growth) is related to abilities for tonal language. Some research has also suggested that certain genes for depression are more likely to be found on the X sex chromosome, making women more prone for this illness than men. 5. Atavism and social darwinism. Atavism is the tendency to revert to traits of ancestors. The social darwinists believed that inferior races displayed atavistic traits and the criminologist Cesare Lombroso claimed that the traits of criminals were atavistic. Their theories have since long been discredited. 6. The selfish gene. The term the "selfish gene" was coined by Richard Dawkins and is a bit misleading. Genes have a tendency to replicate themselves. Through evolution, there has evolved "survival machines" to help genes for that purpose. That is us, animals and plants. What Dawkins means is that we humans are by-products of our genes tendency to replicate themselves. 7. Nature via nurture. As most research suggest that the heritability quotient for most behaviors and personality is between 0.3 and 0.7, it can be assumed that abilities develop through a combination of nature and nurture. For instance, if an individual has inherited genes that makes him physically strong, he may be more likely to enjoy and pursue sports. Similarly, if inherited genes give him an advantage to learn language and music, he may be more inclined for those behaviors. Nature and nurture are equally important for a behavior to develop. Caspi (his first name is Avshalom) and Moffitt have followed a cohort of New Zealand children born in Dunedin in 1972-1973, recording details of their life experiences and testing their DNA. Their findings suggest that individuals may be more at risk to develop certain disorders, but only if there is negative environmental influence. For instance, individuals with a short allele on the 5HTT gene for instance are more likely to develop depression, individuals with a variant of the MAOA gene are more likely to behave antisocially, and a version of the gene COMT increases the risk for Schizophrenia. However, the risk only increased if they had been maltreated as children, had experienced stressful life events or had smoked cannabis as teenagers. 8. One or more genes for behavior? For some rare diseases (such as Huntingson's disease), the cause may be the mutation on one single gene, but for most behaviors there is a plethora of genes interacting. Autism, for example, has been shown to be highly heritable, yet no gene that predispose to this developmental disorder has been found. This suggests either that the development of the disease comes from a multitude of genetic variants or from spontaneous mutations unique to certain families. In most cases, single genes contribute only to slight influences of certain behaviors. 9. Homosexuality and heredity. The Xq28 gene has been linked to homosexuality. Research by Camperio-Ciani (2004) has also suggested that genes that dispose for homosexuality also dispose for high fertility in women (this is why homosexuality does not disappear through natural selection). Female relatives to homosexuals were significantly more fertile than female relatives to heterosexuals. It is also suggested that exposure to high levels of testosterone in the womb may increase chances of homosexuality. Both gay men and women tend to have long ring fingers, which suggests high levels of testosterone in the womb. 10. The genome and medicine. As only twins' genome look exactly the same, drugs can have different effects and side effects on different people. Therefore, doctors and patients usually have to use trial and error to find what works for a patient for a particular drug, such as SSRI:s or antipsychotic medicine (Clorazine has shown to have bad side effects on men with Afro-Caribbean origin). I also know from before that antidepressants have different effects on men and women. 11. Epigenetics. Research has demonstrated that the experiences of your grandparents or earlier generations can have an effect on your genome, switching genes off or adjusting their activity. Child abuse can also create epigenetic effects. Szyf investigated the brains of men who had commited suicide and been abused as children. They had normal genetic sequencing but their epigenetic programming were different from thos that had died from natural causes. 12. Ethical issues of genetics. There are several ethical issues with genetics. One problem is discrimination, for instance its' influence on insurance. For instance, a study has shown that people who have discovered that they have a gene that increases their risk for Alzheimers' disease are more likely to buy insurance to cover long-term nursing care. This may discriminate against other insurance holders, who must pay higher premiums as a result. Those with a proneness for certain diseases may also be discriminated by insurance companies. This is already true for those have a parent with Huntington's disease and insurers often ask about family history before allowing insurance (or raise premiums if the person is at risk for a certain disease). Another ethical issue is genetic determinism. In 1991, Stephen Mobley murdered a man. His lawyers demonstrated that his family had a long history of violent criminals and that he carried a mutation to the MAOA gene that is linked to criminal behavior. Even though the gene does not inevitably lead to crime, it may contribute to it. Some has therefore suggested that research like this can assist in determining degrees of accountability, in a similar fashion to what psychiatric illness does.
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AuthorThis is my class blog for IB Psychology. Here I will publish reflections on psychology, reviews of psychology books, recommended links, lecture notes, and information on psychology topics that are not covered by the syllabus. You are free to add comments or ask me questions. Archives
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