The genetics of sex differences in brain and behavior

Abstract

Biological differences between men and women contribute to many sex-specific illnesses and disorders. Historically, it was argued that such differences were largely, if not exclusively, due to gonadal hormone secretions. However, emerging research has shown that some differences are mediated by mechanisms other than the action of these hormone secretions and in particular by products of genes located on the X and Y chromosomes, which we refer to as direct genetic effects. This paper reviews the evidence for direct genetic effects in behavioral and brain sex differences. We highlight the `four core genotypes' model and sex differences in the midbrain dopaminergic system, specifically focusing on the role of Sry. We also discuss novel research being done on unique populations including people attracted to the same sex and people with a cross-gender identity. As science continues to advance our understanding of biological sex differences, a new field is emerging that is aimed at better addressing the needs of both sexes: gender-based biology and medicine. Ultimately, the study of the biological basis for sex differences will improve healthcare for both men and women.

Civil liability: characterization of the demand for lawsuits against dentists

“…Therefore, even though women outnumber men in the dental profession, men outnumber women as defendants in malpractice lawsuits. This may be due to the psychological and behavioral differences that exist between genders that generally lead to women performing verbal tasks (language and communication) better than men 30 , thereby allowing for an improved relationship with their patients.…”

Homosexuality as a Consequence of Epigenetically Canalized Sexual Development

“…Although pedigree studies indicate a familial association of homosexuality in both males (e.g., Hamer et al 1993) and females (e.g., Pattatucci and Hamer 1995), more than a decade of molecular genetic studies have produced no consistent evidence for a major gene, or other genetic marker, contributing to male homosexuality (reviewed in Ngun et al 2011). Moreover, the most recent genome-wide association study using exceptionally high marker density found no significant association between homosexuality in males and any SNPs (Ramagopalan et al 2010).…”

“…These models are all based on special cases of selection that directly, or indirectly, maintain genetic variation at loci contributing to the homosexual phenotype. However, despite numerous studies over the last decade searching for polymorphisms associated with homosexuality, no convincing molecular genetic evidence has been found despite the fact that pedigree and twin studies clearly show that homosexuality is familial (reviewed in Ngun et al 2011). Homosexuality has also been hypothesized to be caused by nongenetic factors such as maternal antibodies against male-specific antigens (reviewed in Bogaert and Skorska 2011).…”

Is Male Androphilia a Context-Dependent Cross-Cultural Universal?

“…There are three lines of evidence that suggest male androphilia should be present or potentially present in all social systems. The first is strong evidence that male androphilia is heritable through research showing a strong concordance among monozygotic and dizygotic twins compared to unrelated siblings and these rates are greater than the local population average (e.g., Bailey, Dunne, & Martin, 2000;Bailey & Pillard, 1991; for a review, see Ngun, Ghahramani, Sánchez, Bocklandt, & Vilain, 2011). Further, these studies consistently show that male androphilia is more highly heritable in monozygotic twins than in dizygotic twins.…”