Sex linked Inheritance

1
Sex linked Inheritance
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Sex determination

• Sex determination in fruit flies (where it was
  discovered)
• Females have 2 X chromosomes
• Male shave one X and one Y chromosome
• Segregation of the sex chromosomes occurs in
  meiosis
• Morgans famous fruit fly experiment to
  demonstrate sex linked inheritance

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Sex linked genes in humans

• Because males have 1 X chromosome any X linked
  gene is expressed, recessive or not.
• Males pass the X chromosome onto their daughters
  so sex linked genes pass from father to daughter
  and may be expressed in the sons of those
  daughters.

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Sex linked genes in humans

• Colorblindness
• Dominant allele is normal color vision
• Recessive allele causes colorblindness
• 10 of males are colorblind
• Hemophilia
• Blood clotting protein coded for on the X
  chromosome
• Duchenne Muscular Dystrophy
• Protein called dystrophin is missing, causes
  muscles to break down, candidate for gene therapy