Final answer:
In the study of fruit fly genetics, AaBb females have one chromosome with dominant alleles A and B and another with recessive alleles a and b; aabb males contribute one type of chromosome with recessive alleles a and b. The genes are linked, resulting in predominantly parental genotypes unless crossing over occurs.
Step-by-step explanation:
When two genes are located in close proximity on the same chromosome, they are considered linked, and their alleles tend to be transmitted through meiosis together. In the scenario given, an AABB individual is crossed with an aabb individual to produce AaBb females, which are then crossed with aabb males. The AaBb females would have one chromosome carrying the dominant alleles A and B (from the AABB parent), and the other chromosome carrying the recessive alleles a and b (from the aabb parent). The result is a set of chromosomes that can be depicted as:
- Chromosome 1: A B (from AABB parent)
- Chromosome 2: a b (from aabb parent)
In contrast, the aabb males only contribute one type of chromosome, which carries both recessive alleles:
- Chromosome: a b (from aabb)
These parental genotypes are a result of the genes being closely linked, which limits the production of gametes with new combinations of alleles (recombinant gametes). As a result, the expected offspring from the cross of AaBb females and aabb males will mainly exhibit the parental genotypes, unless crossing over between the linked genes occurs.