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Sex Differentiation and Dimorphism

Sex Differentiation and Dimorphism. Sex Differentiation and Dimorphism occurs during……. I n utero Development Adulthood This differentiation and dimorphism arises from circulation of sex steroids Testosterone, Estrogen, Progesterone, 5ɑDHT. The Sex Steroids.

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Sex Differentiation and Dimorphism

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  1. Sex Differentiation and Dimorphism

  2. Sex Differentiation and Dimorphism occurs during…… • In utero • Development • Adulthood • This differentiation and dimorphism arises from circulation of sex steroids • Testosterone, Estrogen, Progesterone, 5ɑDHT

  3. The Sex Steroids

  4. Sex Steroids Invade the Cell Nucleus

  5. Sex Differentiation in utero ….Begins with the presence or absence of the testes-determining SRY gene ..Spontaneous deletion and insertion of SRY gene in mice results in XX mice with testes and XY mice with ovaries

  6. Sex Differentiation in utero Müllerian Ducts WolfianDucts + Secretion of Müllerian Duct inhibiting hormone (MIH)

  7. Sex Differentiation in utero in reptiles is dependent on temperature

  8. What Happens If Sex Differentiation in utero is Disrupted? Great article about these individuals and the science behind the controversy over their biological sex makeup in The New Yorker (2009): http://www.newyorker.com/reporting/2009/11/30/091130fa_fact_levy

  9. Gender Identity Disorders Arising From Improper Sex Differentiation

  10. Sex Differentiation Across Development • can be altered during a “critical period” by hormonal injections, gonadectomy, and subsequent hormone replacement • Historical example: In the 1800s, Roman Catholic Church would castrate young boys to prevent their voice from breaking during puberty since women were no allowed to sing

  11. Organizational vs. Activational Sex Differentiation • Organizational: hormones permanently alters neurochemistry and behavior that persist after puberty (activational period) • Activational: hormones temporarily alter neurochemistry and behavior (for as long as hormone is present)

  12. Experimental Strategy for Delineating Sex Differences in a Neonate

  13. Experimental Strategy for Delineating Sex Differences in an Adult

  14. Sex Differences in Brain Morphology (in the absence of hormone manipulation)

  15. Sex Differences in the Volume or Size of Hypothalamic Centers **differences in synaptic amounts too**

  16. Brains of Gynadomorphs Staining for mRNA encoding for W chromosome This is Pat. His right-side is male (ZZ). His left-side is female (ZW). Staining for mRNA encoding for Z chromosome Agate et al. 2003; PNAS

  17. (Bird) Singing as an Example of Sexual Dimorphism right left HVC: song control nuclei

  18. Sex Differences in the Size of Brain Structures Induced by Hormones

  19. Sex Differences in Neuronal Function Induced by Hormones

  20. Relationship Between Sexual Intercourse and Hormone Circulation • Most non-human females: sexual desire is tightly gated by highly circulating levels of estrogen (“in heat”) • Human females: sexual desire is less associated with circulating estrogen levels but is also influenced by circulating testosterone levels Lordosis: sexually receptive behavior in mammals

  21. Timing is Everything • Treating female mouse with estrogen ONLY= minimal lordosis • Treating female mouse with progesterone ONLY= nothing • Treating female mouse with progesterone THEN estrogen= minimal lordosis • Treating female mouse with estrogen THENprogesterone= full lordosis • Estrogen “primes” (increases the number) of progesterone receptors

  22. Differences in Neuronal Activity with Hormonal Priming

  23. Neurobiological Basis for Homosexuality Size differences in the interstitial nuclei and suprachiasmatic nuclei of anterior hypothalamus LeVay et al. 1991 Swaab and Hofman, 1990

  24. Sex Differences in Size and Presence of Perineal Muscle **Androgen-dependent (organizational)** Anogenital distance: longer in males vs. females

  25. Sex-Specific Behaviors Induced by Hormones

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