Cystic fibrosis Punnett square

GCSE · Combined Science · AQA · B6.1 — Reproduction: sexual vs asexual, meiosis, DNA and the genome, genetic crosses, inherited disorders, sex determination

Question

Cystic fibrosis is caused by a recessive allele (f). Two carriers (Ff) have children.

(a) Draw a Punnett square for this cross. [2] (b) What is the probability of a child having cystic fibrosis? [1] (c) A child is phenotypically unaffected. What is the probability they are a carrier? [1]

4 marks · take your time before peeking.

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