Question

The marriage between first cousins is termed as consanguineous relationship. Such relationships are often strongly discouraged as they lead to an elevated risk of progeny inheriting recessive diseases. If two first cousins are having a child together and they share a grandfather who is a carrier for CF, what is the probability that the child will have CF? Show your calculations.

Answer 1

the mode of inheritance does CF have is Autosomal recessive.

the 3 %,3 in 100 the  risk of a congenital defect in the general population of 2 -3 %

the overall risk of a congenital defect with first cousins is around 6%

but there is still a 94% chance of a normal baby. but the risk of a baby having the recessive condition is higher when the parents of the couple and grandparents are common blood relatives if their family history is having a recessive condition.

here the first cousins share 1/8th of the alleles in common on average bases so there is an increased chance of Autosomal recessive.

if both parents having  Autosomal recessive. there is a chance that the unaffected child has a 2 in 3 chance of becoming a carrier. and also there is 1 in 4 chance  of them having an affected child.