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SEX LINKED TRAITS

SEX LINKED TRAITS. These are the genetic traits often found more in one gender than the other. Every pair of chromosomes in our human cells are identical – except one. The 23 rd pair of chromosomes is different. They either look like an X or a Y. FEMALE = XX MALE = XY.

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SEX LINKED TRAITS

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  1. SEX LINKED TRAITS These are the genetic traits often found more in one gender than the other

  2. Every pair of chromosomes in our human cells are identical – except one. The 23rd pair of chromosomes is different. They either look like an X or a Y. FEMALE = XX MALE = XY

  3. So how is gender determined from a genetic standpoint?Let’s make a Punnett Square. Cross XY x XX

  4. PunnettSquare XY x XX X X X Y

  5. 50% XX 50% XY X X X X X X X X Y X Y Y

  6. 50% XX 50% XY X X X X X X X Girl Girl X Y X Y Y Boy Boy

  7. THE GENES FOR A SEX LINKED TRAIT ARE FOUND ONLY ON THE X CHROMOSOME.

  8. SEX LINKED TRAITS SOME EXAMPLES OF SEX LINKED TRAITS ARE… COLOR BLINDNESS & HEMOPHILIA

  9. THE ALLELES THAT PRODUCE THESE TRAITS ARE RECESSIVE.

  10. FOR A FEMALE TO SHOW ONE OF THESE TRAITS SHE MUST HAVE BOTH RECESSIVE ALLELES (like normal).

  11. FOR A MALE TO SHOW ONE OF THESE TRAITS HE NEEDS TO HAVE ONLY ONE RECESSIVE ALLELE (he doesn’t have another X chromosome to cover it up!).

  12. X This piece is missing

  13. X The gene is on this piece

  14. SEX LINKED TRAITS Let N = normal vision Let n = Color Blind

  15. We put the allele on the X chromosome so we can identify it as a sex-linked trait

  16. A female that has normal vision can have one of these genotypes.

  17. XNXN or XNXn

  18. SEX LINKED TRAITS A male with normal vision can have only ONE genotype

  19. SEX LINKED TRAITS XNY

  20. A female with color blind vision would have ? Genotype?

  21. XnXn

  22. A male with color blind vision would have what Genotype?

  23. XnY

  24. Remember- A male need only have 1 recessive allele to be color blind

  25. SEX LINKED TRAITS Set up a Punnett square to show the following.

  26. Homozygous Normal female & Color Blind male.

  27. XNXN x XnY

  28. Xn Y XN XNXN x XnY Parent cross XN

  29. Xn Y XN XNY XNXn XNXN x XnY XN XNY XNXn

  30. Xn Y XN XNY XNXn XNXN x XnY XN Carrier female Normal male XNY XNXn Carrier female Normal male

  31. Remember – we use the X’s to designate that the gene is sex-linked. Otherwise the Punnett square is just like any other simple dominance problem.

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