Sickle cell anaemia differs from haemophilia in that its gene is carried on:

1. Sickle cell anaemia is controlled by a recessive gene like haemophilia. 2. But that gene sits on an autosome, one of the chromosomes that is not a sex chromosome. 3. So the condition appears with equal frequency in males and females. 4. A genetic cross for it uses ordinary allele letters, with no X or Y attached. 5. Using X and Y chromosomes to represent the sickle cell alleles was the single most common recorded error on this question. _Source: NECTA ACSEE 2023 Biology 133/2, Question 4: Genetics_