Biology 9700 · AS & A Level · Passage of information from parents to offspring
Passage of information from parents to offspring — practice question
The Labrador retriever is a dog breed developed in modern times and may show yellow, black or brown fur, together with pale, black or brown noses. Fur and nose colour are inherited because genes at two separate loci, the B locus and the E locus, interact with one another. Fig. 1.1 shows a Labrador retriever. Table 1.1 shows how gene interaction produces different phenotypes. A male Labrador retriever, heterozygous at the B locus and homozygous recessive at the E locus, was mated with a female Labrador retriever heterozygous at both loci.
(a)[2]
Explain what is meant by the terms locus and homozygous.
(b)[6]
Use a genetic diagram to display the possible genotypes and phenotypes of the offspring from the mating between the two Labrador retrievers. Include the parental phenotypes, parental genotypes, gametes, and offspring genotypes and phenotypes.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “States that locus is the position of a gene on a chromosome” …