Sex differences in behaviour

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what’s sexual differentiation?

Biological developmental process of becoming male or female, begins at fertilisation when chromosomal sex is determined.

What are the stages of sexual differentiation?

• chromosomal sex

• gonadal sex

• morphological sex

• hormonal sex hormones

chromosomal sex?

XX (female) XY (male)

Gonadal sex?

gonads develop into ovaries (females) or testes (male)

morphological sex?

external genitalia develop

hormonal sex

hormones (testosterone or estrogen) influence further development

what happens if the SRY gene is present or absent

SRY gene present- testes form, male development occurs

SRY gene ascent, ovaries form and female development occurs

what happens if the SRY gene is transported to the X chromosome?

an XX individual can develop testes and male genitalia (46, XX testicular disorder of sex development)

role of testoerone and oestrogen un sexual differentiation?

Testoerone: male development promoted by action on Wwolffian duct and masculinising behvaiour

Estrogen: acts on the brain ti masculine behaviour, especially in male rats (aromatisation) testosterone converts to estrogen in the brain

what’s aromatisation in sexual differentiation ?

process owhere testoerone is converted to estradiol (form of estrogen) in the brain, which masculinises the brain and behaviour

how does alpa-fetoprotein protect female foetuses from masculinisation?

alpha-fetoprotein binds ti circulating estrogen, preventing it from affecting the brain of female foetuses, but it doesn’t bind to androgens (like testoerone) allowing male foetuses to be masculinised.

effects of maternal stress on sexual differentiartion?

maternal stress may ,lead to reduced androgen production in male foetuses,which can affect mating behaviour and alter development of male behaviour

difference between organisation and activation effects of sex hormones?

• organization- influences sexual differential during critical periods (prenatal)

• activarional effects (influence behaviour in adulthood (testosterone effects on aggression)

what’s androgen insensitivity syndrome?

A condition where individuals with XY chromosomes do not respond to androgens (male hormones) and develop female external genitalia, despite having testes inside the body

how do endocrine disruptors affect sexual differentiation?

Chemicals (like BPA) can mimic estrogens and interfere with normal hormonal action, potentially masculinizing female brains or altering puberty timing.

what are intra-uterine position effects in rats?

Females positioned near male fetuses in the womb (2-M females) show increased aggression and altered reproductive behavior compared to those positioned in the womb without male fetuses.

What effect does maternal care have on sex differences in behavior?

Mother rats tend to spend more time licking male pups than female pups, and this behavior influences male pup sexual development and future mating behavior.

What is the effect of testosterone exposure on behavior in rats?

Injection of testosterone in neonatal rats can masculinize their behavior, increasing aggression or mating behaviors.

: Can you name a study on sex differences in prenatal hormonal exposure?

• Grady et al. (1965): Found that injecting androgens into rats before 10 days of age caused masculinization of behavior.

• Booth (1977): Found that injecting estrogens into the brain of neonate rats caused even stronger masculinization of behavior.

How does stress affect male fetuses’ development?

Stressed pregnant rats' male fetuses produce less androgen, negatively affecting their mating behavior and reducing rough-and-tumble play later in life.

What are activational effects of sex hormones on behavior in adulthood?

Sex hormones like estrogen and testosterone affect behaviors like aggression, mating, and spatial skills in adulthood by acting on already differentiated brain structures.

What happens to female behavior in males exposed to low prenatal androgens?

Males exposed to low prenatal androgens may show more typically "female" behaviors, such as reduced aggression or less rough play, similar to females in control groups

How does the 2-M effect influence female behavior?

Female rats that are exposed to male fetuses in the womb (2-M females) show higher aggression and longer reproductive cycles compared to other females.

What are SRY gene mutations and their effects?

Mutations in the SRY gene (e.g., Swyer syndrome) result in XY individuals who develop female genitalia and underdeveloped, streak-like gonads (gonadal dysgenesis).

How does prenatal testosterone exposure affect aggression?

Higher prenatal testosterone exposure is linked to more aggressive behaviors in both animals and humans, particularly affecting girls in twin studies (Cohen-Bendahan et al., 2005).

What role does the Wolffian duct play in male sexual differentiation?

The Wolffian duct develops into male sex organs, like the vas deferens and seminal vesicle, under the influence of testosterone during male sexual differentiation.