Hormones and Chromosomes

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Hormones and Chromosomes

• But mostly chromosomes

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23 Pairs of Chromosomes

• 22 autosomes (one pair from mom,dad)
• 23 determines sex
• XYgenetic male
• XXgenetic female
• Actually, any Y will make you a male

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Sperm with X chromosome

• Last longer
• Are larger
• Carry more DNA (2.8 more)

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Y sex chromosomes

• Are smaller
• Swim faster
• Less durable

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Y chromosomes

• Carries very little material what it does seems
  to be
• 1. makes an embryo male
• 2. has a few genes for sperm production
• 3. makes mens ears hairy in middle age

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X chromosome

• Carries about 2,000 genes
• Responsible for a lot of traits
• And in men, all the genes including mistakes and
  recessives show up

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Genes

• Genes come in pairs
• If one of the pair is defective, the other takes
  over
• Usually harmful genes are recessive
• Thus requiring 2 of the bad gene

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But if the X or Y has a defect

• Men will show it
• Such as Duchenne Muscular Dystrophy
• Hemophilia
• Color blindness
• Fragile X syndrome

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XX people dont show it

• Because they have a back up
• A woman could have a defective gene but it will
  not show
• Men have no safety net

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Conception

• 130-150 boys conceived for every 100 girls
• Male fetuses abort more often
• At birth boys outnumber girls 106/100 (acceptable
  range 104-107)
• Boys also have higher incidence of infant
  mortality

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Both XX and XY conceptions

• Start as females (default gender)
• Embryonic body except for 1 X or 1 Y is identical
  
• For 6 weeks
• Fetuses have complete packages of male and
  female interior sexual equipment

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Men you have an interior

• Vagina
• Ovaries
• uterus
• fallopian tubes

13
Women you have an interior

• Seminal vesical for transporting sperm
• A male vas deferens
• But it should come as no surprise that in both
  sexes these things are not functional

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The Mullerian duct

• Grows automatically into a uterus, fallopian
  tubes, and ovaries
• No hormone is necessary (no estrogen necessary)
• Estrogen helps later with secondary sex
  characteristics (breasts)

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What makes a man a man?

• The Y chromosome.

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XY-more complex-2nd trimester

• First, must have a Y chromosome
• The Y brings a gene with it called SRY

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Keep in mind where XX

• Need no hormones for the Mullerian duct to
  develop
• Nor any for the Wolffian to die
• Guys need 2 hormones now

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Wolffian development

• XY need testosterone from testes to make the
  Wolffian duct into
• seminal vesical vas deferens
• AND Mullerian Inhibiting Hormone to kill off the
  Mullerian duct

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For men

• Need masculinization to occur
• And defeminization as well
• Without MIH, the fetus will develop both male and
  female organs

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Exploring MIHs role in other disorders

• Women 2x as likely to have major depression and
  anorexia
• Men are 3x more likely to have dyslexia
• Men are 7x more likely to have autism

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Intersex Conditions
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Many Possibilites

• You can have an infant w/ right side that is male
  and left side that is female
• Or
• Both in one structure, ovotestis

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Hormones

• No known animal w/out estrogen
• Can survive w/out testosterone but you wouldnt
  look male

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Fairly common

• About 1.7 of babies vary from the norm of
  distinct sex
• About as common as cystic fibrosis, half as
  common as Down syndrome

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Androgen insensitive men

• Without male hormones, we are women
• Genetic males who cant utilize androgen
• Thus, appear to be women

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Complete Androgen Insensitivity

• Have breasts, hips, external genitalia
• Secondary sex characteristics fully female
• Secreted a lot of testosterone but it wasnt read
  by the insensitive receptor
• So, it got converted into estrogen and
• These women were more feminine than ever.

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XY Rabbits

• Cut off fetal rabbit testicles
• Rabbits then had vaginas and ovaries
• And could give birth

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CAH girls

• Endocrine disorder
• Congenital adrenal hyperplasia
• Can be in both boys and girls
• But girls have large amounts of male hormone
  before they are born

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CAH girls are often born with

• A penis
• Internal reproductive system is complete and is
  unaffected by male hormone
• So raised as a girl

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But what happened to her brain as an embryo

• She tends to be a tomboy
• She likes rough and tumble games
• She has enhanced spatial skills
• About 37 will be lesbian or bisexual (compared
  to about 2-3 of rest of women)

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Turners syndrome

• X alone written XO
• Infant appears female externally
• Internally Mullerian system degenerated (no
  ovaries)
• short females infertile

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Turners lack estrogen

• Have problems in visual-spatial skills
• Poor in Math
• Non-verbal memory
• Motor impairment

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XXX

• Usually sterile
• Normal in appearance
• 1 in 1,000 girls
• Lower than average language skills
• Poorer memory for recent events
• Perhaps mildly retarded

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XXXX or XXXXX

• Possible as well, serious defects
• Sterile
• Males with XXXY or XXXXY also have severe
  problems in skeletal, reproductive systems

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Klinefelters syndrome XXY

• 1 cases in 500 males
• Male, inside and out
• But small testes can not produce sperm
• Thus, sterile
• Mildly retarded

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XYY Supermales? Not really

• 1 in 700-1,000 males
• Heavy beards, tall
• May be mildly mentally retarded, especially in
  language areas

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Hormones in Humans

• Testosterone does seem to make a difference in
  violence and aggression
• Testosterone 10x greater in men than women
• Other hormones enhance maternal behavior

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Are males more aggressive?

• Humans, maybe
• Other animals, no
• Equal aggressionwolves, shrews, lemurs, and
  gibbons
• Female hyenas are more aggressivebut have less
  testosterone

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Testosterone

• May facilitate aggression
• May also be increased by dominating behavior
• Complex relationship

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Hormones in women

• Often used to make her appear irrational
• When having periods, viewed as emotionally
  erratic
• When not having periods, viewed as emotionally
  erratic
• Hey wait a minute.

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Hormones in women

• Affect women negatively (supposedly)
• But are also used to excuse men for behaving badly

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The Preferred Sex

• Everywhere, Boys
• Extremely so in some cultures

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Boy Preference

• 89 men want a boy, 67 of women
• 54 want boys for first AND 2nd births (Gilroy
  Steinbacher, 1991).
• 1st born sons -100 of non-whites
• 92 of rural respondents, 71 urbans

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Female Infanticide

• 9 of cultures worldwide do this
• No one officially approves of this now
• Female abortions 7,997 out of 8,000 in one study

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How they tell by sex birth ratios

• Normal ratio can be 104-107
• In rural China, now 130-140 to 100
• In Korea SRB 1980 108/100
• By 1985 110/100
• By 1992, SRB for 3rd borns was 196/100 and for
  4th borns 229/100.
• Female-Selective abortion is the only possible
  conclusion