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, displays a wide range of phenotypic variation and has been used in experiments to illustrate inheritance principles.
Most fruit flies have red eyes, although a white-eyed variant also occurs.
Fig. 7.1 shows the red-eyed and white-eyed variants of the fruit fly.
The eye-colour gene is found on the X chromosome.
(a)[5]
Using suitable symbols, draw a genetic diagram to show the possible offspring from a cross between a heterozygous red-eyed female fruit fly and a white-eyed male fruit fly.
(b(i))[1]
State why a man who has haemophilia is unable to pass the condition on to his son.
(b(ii))[1]
Queen Victoria of Great Britain in the 19th century carried haemophilia, but she did not have the condition.
State the term used to describe the genotype of a carrier.
(b(iii))[1]
Neither of Queen Victoria’s parents had the allele for haemophilia.
Suggest how Queen Victoria might have become a carrier.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Appropriate symbols, such as $X^A$ and $X^a$” …