What Is the Probability Dolor and Largo Are Both Carriers of Herrera Syndrome?

[Soaring Crane]

Homework Statement

Dolor and her cousin Largo have conceived a child. They are very concerned about the baby, because they have heard that children of close relatives have a higher incidence of birth defects and/or inherited recessive disorders. They know that their maternal grandmother was a carrier of the Herrera syndrome allele. Assuming that this is the only source of genetic problems for Dolor and Largo, what is the chance that they are both carriers ?
a. 1 in 16

b. 1 in 4

c. 1 in 8

d. 1 in 106

e. 1 in 2

Homework Equations

See below.

The Attempt at a Solution

Each grandchild has ¼ probability of carrying one of four original alleles from grandparents, so the probability of both being carriers is (¼)* (1/4) = 1/16?

Homework Statement

The chance that Dolor and Largo will have a child with Herrera’s
syndrome is
a. 1 in 4

b. 1 in 64

c. 1 in 32

d. 1 in 16

e. 1 in 12

Homework Equations

See below.

The Attempt at a Solution

For the great-grandchild there is a 1/8 probability (of gametes) for getting a recessive allele, so

(1/8) * (1/8) = 1/64?


Thank you for any help.

 

[Moonbear]

Everything sounds right.