Genes and human characteristics

Genes are a fundamental unit of inheritance. Genes can be defined as a sequence of DNA in the genome that is required for production of a functional product. Genes have both minor and major effects on human characteristics. Human genes have become prominent in the nature versus nurture debate. Genes and behavior Genes have a strong influence on human behavior. IQ is largely heritable. However, this has been questioned. The stance that humans inherit substantial behavioral characteristics is called psychological nativism, compared to the stance that human behavior and culture are virtually entirely constructed (tabula rasa). In the early 20th century, eugenics was policy in parts of the United States and Europe. The goal was to reduce or eliminate traits that were considered undesirable. One form of eugenics was compulsory sterilization of people deemed mentally unfit. Hitler's eugenics programs turned social consciousness against the practice, and psychological nativism became associated with racism and sexism. Genes and gender The biggest genetic difference among healthy humans is in gender Scientists debate the extent to which genes and culture affect gender roles. The case of David Reimer was once a case in point for the tabula rasa camp, though recently that same case has become evidence for a strong genetic component to gender identity. Evolutionary psychology Evolutionary psychology explains many human behaviors as more or less moderated by genes that evolved in the hunter-gatherer stage of human cultural development Genetic disorders Main article: Genetic disorder Humans have several genetic diseases, often caused by recessive genes. A few examples of human genetic diseases are: Turner Syndrome, Huntington's disease, cancer, autism, and sickle cell anemia. For a more comprehensive list see List of genetic disorders. Genetic disorders happen everywhere and are very common in some places. • Cri du Chat syndrome – A disorder caused from a deletion on the short arm of chromosome 5. This deletion results in a phenotype of mental retardation, behavioral problems, and a cat like call. About one in every 50,000 births will have the syndrome. • Huntington's disease – A neurological disorder caused by a trinucleotide repeat sequence. Huntingtons is an autosomal dominant trait. Most individuals with the disease will first display the phenotype around 40 years of age. The symptoms are jerky uncontrollable movements, mental retardation, and behavioral problems. • Turner syndrome – A condition that effects females caused by a 45, XO genotype instead of the normal XX genotype. These individuals have only one X chromosome. These individuals are phenotypically female, but will be sterile due to undeveloped ovaries. • Klinefelter syndrome – A disorder in males caused by the presence of an extra X chromosome. These individuals have a genotype of 47, XXY instead of the normal XY genotype. The symptoms for this syndrome are enlarged breasts, small testes, and sterility.