You're on a roll — Step 1: Define the alleles and genotypes. The problem states that normal haemoglobin is Hb$^A$ and abnormal haemoglobin (sickle-cell) is Hb$^S$. Sickle-cell anaemia is due to a recessive gene, meaning Hb$^S$ is recessive to Hb$^A$. Genotypes and their corresponding phenotypes: • Hb$^A$Hb$^A$: Normal (no sickle-cell trait) • Hb$^A$Hb$^S$: Sickle-cell trait (carrier) • Hb$^S$Hb$^S$: Sickle-cell anaemia (affected) The cross is between a man who is heterozygous and a woman who is also heterozygous. Parental genotypes: Man (Hb$^A$Hb$^S$) $\times$ Woman (Hb$^A$Hb$^S$) a) What are the possible phenotypes of the offspring of a man who is heterozygous and a woman who is also heterozygous? Step 1: Perform the cross using a Punnett square. Gametes from each parent are Hb$^A$ and Hb$^S$. $$ \begin{array}{|c|c|c|} \hline \text{Gametes} & \text{Hb}^A & \text{Hb}^S \\ \hline \text{Hb}^A & \text{Hb}^A\text{Hb}^A & \text{Hb}^A\text{Hb}^S \\ \hline \text{Hb}^S & \text{Hb}^A\text{Hb}^S & \text{Hb}^S\text{Hb}^S \\ \hline \end{array} $$ Step 2: Determine the phenotypes from the genotypes. • Hb$^A$Hb$^A$: Normal • Hb$^A$Hb$^S$: Sickle-cell trait • Hb$^S$Hb$^S$: Sickle-cell anaemia The possible phenotypes of the offspring are: $\boxed{\text{Normal, Sickle-cell trait, Sickle-cell anaemia}}$ b) What proportion of the offspring would have been: b) (i) Sickle-cell anaemia? Sickle-cell anaemia corresponds to the genotype Hb$^S$Hb$^S$. From the Punnett square, 1 out of 4 offspring has the genotype Hb$^S$Hb$^S$. The proportion of offspring with sickle-cell anaemia is: $\boxed{\frac{1}{4}}$ b) (ii) Sickle-cell trait? Sickle-cell trait corresponds to the genotype Hb$^A$Hb$^S$. From the Punnett square, 2 out of 4 offspring have the genotype Hb$^A$Hb$^S$. The proportion of offspring with sickle-cell trait is: $\boxed{\frac{2}{4} \text{ or } \frac{1}{2}}$ 4 down, 1 left today. What's next?