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The scenario many of us learned in school is that two X chromosomes make someone female, and an X and a Y chromosome make someone male. These are simplistic ways of thinking about what is scientifically very complex.

0 thoughts on “Sex biology redefined: Genes don’t indicate binary sexes

  1. Isaiah Malefske, PhD, '79

    Dear Madam/Sir:
    In regards to DSD, might I suggest that being 'Transgender' should also be considered as part of this spectrum? Has anyone considered this? Being transgendered myself since my earliest memories (18 months old or less) and now in my 60's, my biology regarding sex, gender has never been socially accepted, and until recently not even addressed by the conservative medical/scientific community.
    Does anyone have any input in this matter?

  2. Zoe Brain

    Dr Malefske has a point in view of these findings;

    Male–to–female transsexuals have female neuron numbers in a limbic nucleus. Kruiver et al J Clin Endocrinol Metab (2000) 85:2034–2041
    The present findings of somatostatin neuronal sex differences in the BSTc and its sex reversal in the transsexual brain clearly support the paradigm that in transsexuals sexual differentiation of the brain and genitals may go into opposite directions..

    A sex difference in the human brain and its relation to transsexuality. by Zhou et al Nature (1995) 378:68–70.
    Our study is the first to show a female brain structure in genetically male transsexuals...

    White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study. - Rametti et al, J Psychiatr Res. 2010 Jun 8.
    CONCLUSIONS: Our results show that the white matter microstructure pattern in untreated FtM transsexuals is closer to the pattern of subjects who share their gender identity (males) than those who share their biological sex (females)