03 sex linked inheritance

2,220 views
1,732 views

Published on

Published in: Education
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,220
On SlideShare
0
From Embeds
0
Number of Embeds
11
Actions
Shares
0
Downloads
0
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

03 sex linked inheritance

  1. 1. SEX-LINKED TRAITS
  2. 2. SEX-LINKED TRAITS Male and female genotypes… XY XX
  3. 3. SEX-LINKED TRAITS How is sex determined? X Ya In this case, Y female child will result XX X Y X
  4. 4. SEX-LINKED TRAITS How is sex determined? X Ya In this case, Y male child will result XY X Y X
  5. 5. SEX-LINKED TRAITSThe X-chromosome may contain alleles for the following:-Hemophilia-Colour blindness-Baldness-Duchenne muscular dystrophy These X-linked recessive “disorders” predominantly affect males.
  6. 6. SEX-LINKED TRAITSFemales have two X chromosomes, so the X-linked recessive diseases will not affect them. XX XX H XX C XX BPhenotype: Normal Normal Normal Normal
  7. 7. SEX-LINKED TRAITSHowever, males only have one X-chromosome… XY X HY XC Y X BY
  8. 8. SEX-LINKED TRAITS However, males only have one X-chromosome… XY X HY XC Y X BYPhenotype: Normal Hemophiliac Colour blind Bald
  9. 9. SEX-LINKED TRAITS So how is baldness inherited?XXB XY X Y X XX XY X B XXB XBY F1 Genotypes: 25% XX, 25% XXB, 25% XY, 25% XBY F1 Phenotypes: 50% of males are bald. Females are “normal” (wild type)
  10. 10. SEX-LINKED TRAITS The female with the genotype XXB will not become bald, BUT she is a carrierShe can passthe baldnessallele to her XXB XXBoffspring
  11. 11. SEX-LINKED TRAITSIt is possible for women to be bald, too!
  12. 12. SEX-LINKED TRAITS How is this possible?!If the father is bald, and the mother is a carrier, then half of her children will become bald XXB XBY XB Y X XXB XY X B XBXB XB Y
  13. 13. SEX-LINKED TRAITS How is this possible?!If the father is bald, and the mother is a carrier, then half of her children will become bald It is very rare for a women to be bald. Why did I It’s not fair! have to be one of me Don’t get them?!! started… XXB XB XB XY XBY F1 Genotypes: 25% XXB, 25% XBXB, 25% XY, 25% XBY F1 Phenotypes: 50% of male and female offspring are bald
  14. 14. SEX-LINKED TRAITS So how is hemophilia inherited?In the same way as baldness, hemophilia is inherited usually because the mother is a carrier. Once again, usually male children are affected X Y X XX XYXX H XY X H XXH XH Y
  15. 15. SEX-LINKED TRAITS Sample question:If a hemophiliac man has children with a “normal” woman (who is NOT a carrier),a) What is the probability of having kids that will develop hemophiliab) What is the probability of female kids being carriers? XH Y X XXH XYa) _______________________ 0% chance of kids having X XXH XY hemophilia_________________________ 100% of females will be carriersb) ______________________________________________________

×