Kathy's brother has cystic fibrosis. Her husband has no family history of CF. What is the chance that Kathy's child has inherited cystic fibrosis?
Correct answer: D. 2/3 x 1/2 = 1/3
- A. 1/2x 1/2 = 1/4
- B. 1/3 x 1/2 = 1/6
- C. 2/3 x 1/4 = 1/6
- D. 2/3 x 1/2 = 1/3
Explanation
Cystic fibrosis is an autosomal recessive disorder. If Kathy is a carrier, there is a 50% chance she will pass on the CF allele to her child. Therefore, there is a 25% or 1/4 chance that Kathy's child is a carrier of the CF mutation, assuming Kathy's husband does not carry the CF mutation.
Last updated
About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
Practise Inheritance
1,238 free Inheritance MCQs from Biology, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Biology questions like this
Biology is on 6 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
4 Mutations in opsin genes cause_ types of colorblindness.
9 : 3 : 3 : 1 ratio is given by:
A bald man marries to pattern bald woman. The chance of baldness in their daughter is:
A botanist sees that when he breeds a plant with blue flowers and a plant with red flowers, the resulting generation are plants with a 1:1 ratio of blue: red flowers. He knows that the two parents are homozygous for the trait of color. What phenomenon most likely explains the 1:1 ratio in the filial generation?
A carrier female for hemophilia can pass the defective allele to: