Genetic terms and monohybrid inheritanceAQA A-Level Biology: Mind map

Exam questions on Genetic terms and monohybrid inheritance

1. In shorthorn cattle, coat colour is controlled by a single gene with two alleles, $C^R$ (red hairs) and $C^W$ (white hairs). The alleles are codominant. Animals with both alleles have a roan coat, with a mixture of red and white hairs.
   A red bull is crossed with a white cow. Predict the phenotype of the calves and explain your answer.2 marks
2. Cystic fibrosis is caused by a recessive allele, $f$, of a gene on chromosome 7. The dominant allele, $F$, codes for a functioning chloride ion channel. Two healthy parents, who have both already had one child with cystic fibrosis, plan to have more children.
   The couple go on to have two more children. Calculate the probability that both children have cystic fibrosis.2 marks
3. In pea plants, tall stems are produced by the dominant allele $T$ and dwarf stems by the recessive allele $t$. A plant breeder crosses a tall plant of unknown genotype with a dwarf plant. The offspring are 48 tall plants and 52 dwarf plants.
   Deduce the genotype of the tall parent and explain how you reached your answer.3 marks