Biology 9700 · AS & A Level · Passage of information from parents to offspring
Passage of information from parents to offspring — practice question
The fruit fly, Drosophila melanogaster, feeds on sugars present in damaged fruit. A fruit fly showing normal characteristics is called wild type. It has red eyes and wings that are longer than its abdomen. Mutant forms include flies with purple eyes or short (vestigial) wings. Fig. 7.1 shows a wild type fruit fly and a mutant fruit fly with purple eyes and vestigial wings. The genes coding for eye colour and wing length are located on the same chromosome. Allele R for red eyes is dominant to allele r for purple eyes. Allele N for long wings is dominant to allele n for vestigial wings.
(a)[2]
Explain what the terms allele and dominant mean.
(b(i))[5]
A wild type fruit fly that is heterozygous for both genes was crossed with a fruit fly homozygous recessive for both genes. Table 7.1 summarises this cross. Complete Table 7.1.
(b(ii))[3]
Explain why the four offspring phenotypes do not occur in a $1:1:1:1$ ratio.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “An allele is an alternative version/form of a gene” …