Final answer:
The genetic difference between fruit flies can vary based on gene expression in different conditions. For a cross between a white-eyed male and a heterozygous red-eyed female, the offspring's eye color ratio would be 1:1. Reproduction research shows that mating has a cost on fruit fly lifespan and energy resources.
Step-by-step explanation:
The amount of genetic difference between individual fruit flies (Drosophila melanogaster) can vary. Although all fruit flies have the same genetic makeup, they express different patterns of genes under various environmental conditions. For example, specific genes may be expressed in cold conditions while others may be expressed in warm conditions. This represents phenotypic plasticity rather than genetic difference.
In terms of inheritance, if a cross is made between a white-eyed male fruit fly and a heterozygous female for red eye color (X^W X^w), the offspring would be expected to follow a Mendelian inheritance pattern. The ratio of the offspring's eye color would be 50% red-eyed females (X^W X^w), 50% white-eyed males (X^W Y), 50% red-eyed males (X^w Y), and 50% white-eyed females (X^W X^W). This is because eye color in fruit flies is a sex-linked trait with the gene for eye color being located on the X-chromosome.
Research into fruit fly reproduction has revealed that there is a cost to reproduction in terms of lifespan in male fruit flies and that mated flies have limited sperm remaining for further mating attempts. Selection for certain traits, such as resistance or susceptibility to DDT, can also affect reproductive rates such as egg production.