Pearson Edexcel GCSE (9-1) Biology practice

Cystic fibrosis is a genetic disorder caused by a recessive allele (f). Individuals with at least one dominant allele (F) do not have the condition. A couple, both of whom are carriers for cystic fibrosis, decide to have children. a) Draw a Punnett square to show the possible genotypes and phenotypes of their offspring. b) Calculate the probability, as a percentage, that their first child will: i) have cystic fibrosis. ii) be a carrier for cystic fibrosis. c) Explain how pedigree analysis could be used to determine if a family trait is dominant or recessive, even without genetic testing. [9 marks]

Try the question first, then check the answer and practise the same topic again.