Pedigrees

1. Pedigrees

2. First Decision Is it autosomal or X-linked inheritance? Autosomal: both genders are equally affected; male-to-male transmission observed If not, propose X-linkage

3. Second Decision Is it dominant or recessive? Dominant: trait does not usually skip generations; each person with at least one copy of the dominant allele will show the trait If not, propose recessiveinheritance

4. Autosomal Recessive • Males and females are equally likely to have the trait • Traits often skip generations • Often, both parents of the offspring who have the trait are heterozygotes • Only homozygous individuals have the trait • Traits may appear in siblings without appearing in their parents • If a parent has the trait, those offspring who do not have it are heterozygous carriers • Autosomal Dominant • Males and females are equally likely to have the trait • Traits do not skip generations • The trait is present whenever the corresponding gene is present • Male to male transmission

5. X-linked Recessive • Trait is more common in males than females • All daughters of a male who has the trait are heterozygous carriers • The son of a female carrier has a 50 percent chance of having the trait • No male-to-male transmission • Mothers of male who have the trait are either heterozygous carriers or homozygous and express the trait • Daughters of female carriers have a 50 percent chance of being carriers • X-linked Dominant • All daughters of a male who has the trait will also have the trait • No male to male transmission • A female who has the trait may or may not pass the gene to her son or daughter

6. Scenario 2, Page 1-29 of Lab Manual • Joseph and Jenny have come to a genetic counselor to determine their chances of having a child with myotonic dystrophy, a degenerative muscular disorder that appears at about 50 years of age and is inherited with the autosomal dominant allele D. The autosomal recessive allele d does not contribute to the development of the disease. Both Joseph and Jenny are in their thirties and neither shows any signs of the disease at present. Jenny’s grandmother (her father’s mother) has the disease. Jenny’s grandmother’s father (Jenny’s great-grandfather) did not have the disease. There is no history of myotonic dystrophy in Joseph’s family or in Jenny’s mother’s or paternal grandfather’s family. • Draw the pedigree that shows the familial relationships described in the paragraph above. • What is the probability that Jenny is a carrier of the D allele? • What is the probability that Joseph and Jenny will have a child with myotonic dystrophy? • Out of 3 children born to Joseph and Jenny, what is the probability that 1 will have myotonic dystrophy? • Out of 5 children born to Joseph and Jenny, what is the probability that at least one will have myotonic dystrophy?

7. Scenario 4, Page 1-30 of Lab Manual • Alkaptonuria is a metabolic disorder that results from the autosomal recessive allele a. Individuals who do not have the disease have the dominant allele A. Nancy, who does not have alkaptonuria, marries Norman, who also does not have alkaptonuria. Norman’s grandmother (his father’s mother) and Nancy’s uncle (her mother’s brother) have alkaptonuria. Norman’s grandfather (his father’s father) does not have the disease and is not a carrier of the alkaptonuria allele. Neither of Nancy’s maternal grandparents (her mother’s mother and father) have alkaptonuria. There is no history of alkaptonuria in Norman’s mother’s family or in Nancy’s father’s family. • Draw the pedigree that shows the familial relationships described in the paragraph above. • What is the probability that Nancy is a carrier of the a allele? • What is the probability that Norman is a carrier of the a allele? • What is the probability that Nancy and Norman’s first child will have alkaptonuria? • Out of 5 children born to Nancy and Norman, what is the probability that 3 will have alkaptonuria? • Out of 4 children born to Nancy and Norman, what is the probability that at least one will have alkaptonuria?

8. Scenario 6, Page 1-31 of Lab Manual • Red-green colorblindness is inherited with the X-linked recessive allele c. The X-linked dominant allele C codes for full color vision. John is colorblind. His wife Jean has full color vision. Both of Jean’s parents and both maternal grandparents (Jean’s mother’s parents) have full color vision but her great grandfather (the father of Jean’s maternal grandmother) is colorblind. There is no history of colorblindness in Jean’s father’s family. • Draw the pedigree that shows the familial relationships described in the paragraph above. • What is the probability that Jean is a carrier of the c allele? • Out of 3 children born to Jean and John, what is the probability that 2 will be colorblind sons? • Out of 4 children born to Jean and John, what is the probability that at least one will be a colorblind daughter?