Biology 9700 · AS & A Level · Passage of information from parents to offspring
Passage of information from parents to offspring — practice question
Individuals differ in the molecules found on the surface of their red blood cells. For instance, in the ABO blood group system, people can be classified as one of four blood groups: A, B, AB and O. A single gene, $I$, with three alleles, controls these blood groups. Gene $I$ is an example of a gene with multiple alleles. Alleles $I^A$ and $I^B$ are codominant. Allele $I^o$ is recessive to alleles $I^A$ and $I^B$.
(a)[3]
Explain the meaning of codominant and recessive.
(b)[3]
Table 7.1 presents a cross between a person with blood group A and a person with blood group B. Complete Table 7.1.
(c)[3]
Haemophilia is a blood disorder in which bleeding continues for a long period of time after a blood vessel has been damaged. A person with haemophilia has a mutation in a gene on the X chromosome, which leads to the lack of a blood clotting factor. Explain why a man who has haemophilia cannot pass the condition to his male offspring.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “codominant alleles are both expressed in a heterozygote” …