Biology 9700 · AS & A Level · Passage of information from parents to offspring
Passage of information from parents to offspring — practice question
In the fruit fly, Drosophila melanogaster , body colour and eye colour are each governed by a different gene. G/g are alleles of the body colour gene, with G producing a grey body and g producing a black body. R/r are alleles of the eye colour gene, with R producing red eyes and r producing brown eyes. Both genes are autosomal. A dihybrid cross was done using a fly with a grey body and red eyes and a fly with a black body and brown eyes. Both parents were homozygous for both genes. The F1 offspring were crossed to produce the F2 offspring.
(a)[2]
A statistical test indicated that the cross results were significantly different from those expected. State the name of the statistical test used and state the expected phenotypic ratio for the F2 generation.
(b)[4]
A test cross can be used to identify flies from an F2 generation that are heterozygous for both genes. Draw a genetic diagram to show how a test cross between a heterozygous grey-bodied, red-eyed F2 fly and a fly with a black body and brown eyes can produce four different offspring phenotypes. Use the symbols G/g and R/r.
(c)[5]
The results of the test cross in (b) are presented in Table 2.1. They are significantly different from the expected results. Describe how these results differ from the expected results and explain why they differ.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Chi-squared test $(\chi^2)$ named” …