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Sex-linked Traits

Sex-linked Traits. Sex determination. Sex chromosomes – determines the sex of an individual Y X Males have X and Y Two kinds of gametes Female have two X’s Only one type of gamete. Which parents determines the sex of the offspring?. XY male. X. Y. XX Female. X. X.

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Sex-linked Traits

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  1. Sex-linked Traits

  2. Sex determination • Sex chromosomes – determines the sex of an individual • Y • X • Males have X and Y • Two kinds of gametes • Female have two X’s • Only one type of gamete

  3. Which parents determines the sex of the offspring? XY male X Y XX Female X X It is the male that determines the sex of the offspring.

  4. Sex Linked Traits • Traits controlled by genes located on sex chromosomes (X or Y) • Most are X-linked • The X chromosome is larger and has more genes • A Y has very few genes • Show inheritance pattern that differs for autosomal traits.

  5. X-linked Inheritance

  6. Males only have one copy of the X chromosome (hemizygous),plus a Y • Female have two X chromosomes, and may be homozygous or heterozygous for a trait • X-linked genes are never passed from father to son. The Y chromosome is the only sex chromosome that passes from father to son.

  7. Females with one copy of the normal gene and one copy of the mutated gene are called carriers. They don’t show the trait. • Males are never carriers – if they have a mutated gene on the X chromosome, it will be expressed

  8. X-linked disorders • Recessive • Red-green color blindness • Hemophilia • Duchenne muscular dystrophy • Ichthyosis • Dominant • Hypertrichosis

  9. Red-green color blindness • Can not distinguish red from green. Normal red-green Red-green colorblind

  10. What a red-green colorblind person would see Normal Red-green colorblind

  11. X Chromosome Inactivation • While females have two X chromosomes, only one is active. • The other is turned off. • This is random, in some cells the maternal X is turned off and in others the paternal X is turned off. • All descents of that cell will have same X turned off • It is condensed and known as a Barr Body.

  12. Hemophilia

  13. Non-carrier Mother + Father With Hemophilia

  14. Carrier Mother + Non-hemophiliac Father

  15. Carrier Mother + Father With Hemophilia

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