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SEX LINKED INHERITANCE

SEX LINKED INHERITANCE. Sex Determination: The human XY system Nondisjunction: The failure of chromosomes to separate properly during one of the stages of meiosis (fig. 11-12) This can produce gametes w/two sex chromosomes or no sex chromosomes. Results in abnormal # of sex chromo.

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SEX LINKED INHERITANCE

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  1. SEX LINKED INHERITANCE Sex Determination: The human XY system Nondisjunction: The failure of chromosomes to separate properly during one of the stages of meiosis (fig. 11-12) This can produce gametes w/two sex chromosomes or no sex chromosomes. Results in abnormal # of sex chromo. Nondisjunction disorders Turner syndrome- female in appearance, w/o sex organs 45X or 45XO Klinefelter syndrome- Male in appearance, sterile, 47XXY Babies are not born without an X chromosome What can we learn? X chromo. Is essential; gender is determined by presence/absence of Y

  2. NONDISJUNCTION DISORDERS

  3. SEX-LINKED INHERITANCE

  4. SEX-LINKED GENETIC DISORDER • Sex-linked: Genes carried on the X or Y Chromo. Which are expressed more commonly in males. WHY? • COLORBLINDNESS- Most caused by genes located on X chromo. • Red-green is most common, 8% males; 1% females • Carried on X chromo.; dominant allele is XC & recessive is Xc. • Why more common in males? • HEMOPHILIA- Bleeders disea • se, protein AHF is missing. • MUSCULAR DYSTROPHY- Progressive wasting away of muscle. • Caused by defective version of the gene, dystrophin • SEX-INFLUENCED TRAITS: Caused by a gene whose expression differs in males & females, located on autosomes.

  5. SEX-LINKED DISORDERS

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