of extra chromosome o Typically, less muscular/less body hair, increased breast tissue due to lower testosterone production Sexual differentiation occurs after the first six weeks of development duct systems for both sets of sex organs are present + gonads o SRY mediates sexual differentiation because of TDF which causes gonads to produce testosterone T then determines duct development o Mullerian duct forms the fallopian tubes, uterus and upper part of vagina Develops in absence of testosterone Wolffian duct degenerates o Wolffian duct forms the vas deferens, epididymis, seminal vesicle and ejaculatory duct Develops in presence of testosterone also promotes production of Mullerian-inhibiting factor (MIF) Mullerian duct degenerates o Hermaphroditism occurs when external genitals are undetermined or in an intermediate form due to hormonal irregularities during differentiation stage of development Sex hormones belong to the steroid class of hormones synthesized from cholesterol o Each have a four-carbon ring-structure small chemical changes to base molecule causes profound consequences for effects of sex hormone Males produce more androgens testosterone Released by testes and adrenal glands Responsible for masculinization females have 1/10 th amount Levels surge prenatally during primary differentiation and at puberty during development of secondary sex characteristics Females produce more estrogens and progestins estradiol/estrone, progesterone Released by ovaries Estrogen levels surge during puberty to control maturation of reproductive cycle and breast development Progesterone levels increase during pregnancy Female hormones follow 28-day estrus cycle o Most hormones are peptides and therefore cannot readily cross the cell membrane steroids are fat soluble and thus easily cross the lipid bilayer Steroids act on intracellular receptors within the cytoplasm directly affect gene expression Different tissues express internal receptors differently, so respond to the effects of sex hormones differently o Ex. Breast tissue has a strong response to estrogens
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- Winter '18
- Y chromosome