Question

A man who has cystic fibrosis married a healthy women. They produce 2 children who both have cystic fiber. What are the genotypes of the man and women? (use symbols to represent the alleles and which parent is which)

Answer 1

Answer:

The correct answer would be -

Father - both alleles are recessive for the gene - cc

Mother - carrier with the heterozygous condition - Cc

Explanation:

Cystic fibrosis is a recessive genetic disease that means it exhibits only if both copies of the gene mutated, If there is only one copy of the gene is mutated the person will be healthy however, he or she will be a carrier of the mutated gene.

Given: Father has cystic fibrosis which means he has two copies of the mutated gene - cc (c - recessive)

Female - she is healthy now there is two conditions possible

1. if the mother is healthy -  CC (normal allele)

  C     C

c Cc  Cc

c  Cc  Cc

All offspring are in the heterozygous condition that means they are healthy carriers which is not given in the question so women must be a carrier

2. Carrier mother -  Cc

   C     c

c    Cc  cc

c   Cc   cc

Here 50% chances of having children with CF so it is possible as two offsprings have CF according to question

Thus, Father - both alleles are recessive for the gene - cc

Mother - carrier with the heterozygous condition - Cc