Genetics and Orientation


Dr. Cynthia Chappell discusses the results of family and twins studies that point to the link between genes and sexual orientation.


Genes are involved in sexual orientation.

Pedigree Studies

Pedigree studies are studies that look at families with two or more gay children and explore the incidence of homosexuality in maternal and paternal family histories. Birth order studies look at the incidence of homosexuality and birth order. Twin studies are studies that look at incidence of homosexuality in families where there are twins. Family studies have indicated that a genetic link is likely.

Molecular Studies (Chromosomal Areas)

Family studies pointed to a genetic component to sexual orientation. Molecular studies sought to find chromosomal areas in which genetic links occur.

  • Genetics
  • Linkage Studies – Linkage studies within identified chromosomal areas indicate that a genetic link does exist supporting the likelihood that homosexuality had genetic influences.
  • Genome-wide Studies – As our techniques have improved, we now have the ability to look at whole genomes at the same time and more links have been identified, further supporting a genetic link to sexual orientation.

 Linking Genes to Proteins

Some of the areas that have been identified as  links to sexual orientation are areas that are responsible for significant areas of known brain differences and regulatory proteins.

Review of Lesson 203

What are your thoughts? What questions do you still have?

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