1. Sex-Linked Inheritance

2. Certain traits are carried on the ‘X’ chromosome. Certain traits are carried on the ‘X’ chromosome. These traits are recessive. These traits are recessive. Examples include; baldness, colour- blindness, and haemophilia. Examples include; baldness, colour- blindness, and haemophilia.

3. Sex-Linked Inheritance For a female to express the phenotype she must have the allele on both her X chromosomes. For a female to express the phenotype she must have the allele on both her X chromosomes.

4. Sex-Linked Inheritance For a female to express the phenotype she must have the allele on both her X chromosomes. For a female to express the phenotype she must have the allele on both her X chromosomes.Normal X X X X

5. Sex-Linked Inheritance For a female to express the phenotype she must have the allele on both her X chromosomes. For a female to express the phenotype she must have the allele on both her X chromosomes. Normal Colorblind X X X c X c X X X c X c

6. Sex-Linked Inheritance For a female to express the phenotype she must have the allele on both her X chromosomes. For a female to express the phenotype she must have the allele on both her X chromosomes. Normal Colorblind Carrier X X X c X c X c X X X X c X c X c X

7. Sex-Linked Inheritance However, a male will express the phenotype if the allele is on his single X chromosome. However, a male will express the phenotype if the allele is on his single X chromosome.Normal X Y X Y

8. Sex-Linked Inheritance However, a male will express the phenotype if the allele is on his single X chromosome. However, a male will express the phenotype if the allele is on his single X chromosome. Normal Colourblind X Y X c Y X Y X c Y

9. Sex-Linked Inheritance However, a male will express the phenotype if the allele is on his single X chromosome. However, a male will express the phenotype if the allele is on his single X chromosome. Normal Colourblind Carrier X Y X c Y n.s.t. X Y X c Y n.s.t.

10. Sex-Linked Inheritance It is much less likely for females to have sex- linked diseases than males because they need to inherit the allele from both of their parents in order to have the disease. It is much less likely for females to have sex- linked diseases than males because they need to inherit the allele from both of their parents in order to have the disease.

11. Sex-Linked Inheritance It is much less likely for females to have sex- linked diseases than males because they need to inherit the allele from both of their parents in order to have the disease. It is much less likely for females to have sex- linked diseases than males because they need to inherit the allele from both of their parents in order to have the disease. Males only need to acquire one affected X chromosome to have the disease because the Y chromosome does not have a healthy allele to compensate. Males only need to acquire one affected X chromosome to have the disease because the Y chromosome does not have a healthy allele to compensate.

14. The End