Question 1
Paper 2Medium16 marksIn a beetle species, allele A gives a dark body and allele a gives a pale body. Allele B gives long antennae and allele b gives short antennae. A and B are completely dominant to a and b, respectively.
A homozygous dark-bodied, long-antennaed beetle (AABB) is crossed with a homozygous pale-bodied, short-antennaed beetle (aabb). An F₁ beetle is testcrossed with an aabb beetle. The following offspring are recorded.
| Offspring phenotype | Number |
|---|---|
| Dark body, long antennae | 416 |
| Pale body, short antennae | 404 |
| Dark body, short antennae | 92 |
| Pale body, long antennae | 88 |
State the genotype of the F₁ beetle and the arrangement of its alleles on its homologous chromosomes.
Assuming the genes assort independently, determine the gamete types produced by the F₁ beetle and the expected offspring genotypes and phenotypes from the testcross. State the expected phenotypic ratio.
Using the observed offspring, identify the recombinant gamete types from the F₁ beetle and their corresponding offspring genotypes and phenotypes.
Identify the parental offspring phenotype and genotype classes. Compare the observed results with the expected outcome if the genes assort independently, and infer whether the genes are linked.