Sex-Linked Traits

Inheritance of Traits  X-linked Disorders - occur mainly in males because the mother usually donates the recessive allele and males have only one X chromosome.  Carriers – are individuals who are heterozygous for an inherited disorder but do not show symptoms of the disorder; they can pass the allele for the disorder to their offspring

X-Linked Traits  Colorblindness is an X-linked recessive disorder. ex: X X - female, normal X c X - female, normal (carrier for colorblindness) X c X c - female, colorblind X Y - male, normal X c Y - male, colorblind

Colorblindness is an X-linked recessive disorder. Show a cross between a X c X and a XY. XcXc X X Y

X-Linked Traits  Hemophilia is an X-linked recessive disorder. ex: X X - female, normal X h X - female, normal (carrier for hemophilia) X h X h - female, hemophilia X Y - male, normal X h Y - male, hemophilia

X X X Y Show a cross between a female who is a carrier of hemophilia with a male who has the disorder.

Hemophilia is x-linked recessive. Suppose that a man with hemophilia marries a woman who does not have the disorder. What are the chances that their offspring will have hemophilia?

Cystic Fibrosis is an autosomal recessive disease. Suppose that a man with a family history of CF marries a woman with no history of the disease. The woman has no genes for CF while the man is a carrier (heterozygous) and does not have the disease.  If these people become parents, what are the chances that their children will have CF?

Huntington’s is a dominant disorder.  Suppose that a man with two children, aged 15 and 17, develops Huntington’s disease at age 50. The man is heterozygous and his wife does not have the disease. What are the chances that the children will have this disease?

Blood type inheritance is somewhat complicated, with three forms of the gene and 4 possible phenotypes. (A, B, AB, O)  AB  Homozygous A (AA)  Heterozygous A (AO)  Homozygous B (BB)  Heterozygous B (BO)  OO

Blood Types: Suppose a woman with blood type AB marries a man with type BO. What are the chances that their children will have blood type A? blood type B? blood type AB?

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