Question

You have been hired to produce a family tree for three generations of a family where a disorder called sneezer syndrome is observed. People who suffer from sneezer syndrome sneeze when they smell peppermint. In order to draw a pedigree chart for this family, you interview Mike and Annie. Neither suffer from sneezer syndrome. Annie’s mother is normal, while Annie’s father sneezed at the smell of peppermint. Annie has one sister and one brother and her sister is a sneezer. While Annie’s sister has yet to have kids, her brother married a sneezer. Mike’s mother is a sneezer while his father is normal. Mike’s brother is just like their mother. In addition, this brother married a sneezer. Mike’s sister is normal - as is her husband and their one boy.

draw a pedigree chart (one point). Use the letters A and a. If more than one genotype is possible for an individual - you may write it as A with a dash - e.g. A-

Use your pedigree chart to answer the following questions (four points):

a. Annie’s brother and his wife have two kids – a sneezing boy and a normal girl. What are their genotypes ?

boy -

girl -

b. What are the genotypes of Mike’s brother-in-law (his sister’s husband) and their boy?

brother-in-law -

his son -

c. Mike and Annie have two girls and a boy. The boy and one girl are normal. What are the genotypes of their three kids?

boy -

girl 1 -

girl 2 -

d. Mike and Annie want a 4th child. What is the chance that this child will be a boy who is a sneezer. Write your answer as a reduced fraction - e.g. 1/8.

Answer 1

a. Annie’s brother and his wife have two kids – a sneezing boy and a normal girl. What are their genotypes ?

Answer: Boy (aa) and Girl (A-), explained in image Case-IV

b. What are the genotypes of Mike’s brother-in-law (his sister’s husband) and their boy?

Answer: brother-in-law (A-) and his son (A-), explanation in image Case-III.

c. Mike and Annie have two girls and a boy. The boy and one girl are normal. What are the genotypes of their three kids?

Answer: boy & girl 1 will have (A-) and girl 2 will have (aa)

d. Mike and Annie want a 4th child. What is the chance that this child will be a boy who is a sneezer. Write your answer as a reduced fraction - e.g. 1/8.

Answer: 1/4

For this case, the chance will be 1/4 for affected male (aa). Here, the cross will be between Aa and Aa. And the genotype will be in ratio AA:Aa:aa (1: 2: 1) respectively. Hence chances of affected child are 1 out of 4 i.e. 1/4.

Good Luck!!!!!

Thanks!!!!