The locus is autosomal and the mutation that causes alkaptonuria is recessive. K
ID: 3164442 • Letter: T
Question
The locus is autosomal and the mutation that causes alkaptonuria is recessive. Key role of first cousins mating (show pedigree). Firsdt cousins share two grandparents. If one of the grandparent is a heterozygote for alkaptonuria, what is the probability that an offspring of the first cousins is homozygous fro alkaptonuria- becasue both cousins inherited a copy of the alkaptonuria allele from the heterozygous grandparent?
The anwer is (1/2)6
I'm having trouble understanding how to solve these types of problems. If possible, Please show every step and include explanation. Thanks.
Explanation / Answer
Alkeptoneuria is an autosomal recessive disease. Now the both cousins have the recessive trait.
Female cousin genotype = A’A +XX
Male cousin genotype= A’A +XY
The A’ is showing the trait of the recessive disease.
Now cross between both cousins-
Gametes
A’+X
A’+Y
A+X
A+Y
A’+X
A’A’+XX
A’A’+XY
AA’+XX
AA’+XY
A+X
AA’+XX
AA’+XY
AA+XX
AA+XX
NOW, THE homozygous Alkeptoneuria is present in two children. Therefore, the probability is 2/8 =1/4.
Gametes
A’+X
A’+Y
A+X
A+Y
A’+X
A’A’+XX
A’A’+XY
AA’+XX
AA’+XY
A+X
AA’+XX
AA’+XY
AA+XX
AA+XX
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