The 1:1 ratio of flies with normal eyes/normal wings to flies with purple eyes/vestigial wings can be accounted for by the fact that the genes for eye color and wing size are located close together on the same chromosome. Here's why:
1. Because the space on the chromosome of each gene is very close (genes that are close together on the same chromosome are likely to stay together during division), the genes for eye color and wing size are inherited together more often than not.
2. This close proximity of the genes on the chromosome results in them being inherited in a linked manner, meaning that the alleles for normal eyes and normal wings are inherited together, as well as the alleles for purple eyes and vestigial wings.
3. Due to this linkage, when flies undergo genetic recombination during meiosis, there is a tendency for the alleles of the two genes to stay together and not undergo crossing over to separate them onto different chromosomes.
4. As a result, the 1:1 ratio observed is due to the linked inheritance of these genes on the same chromosome, leading to a higher likelihood of flies inheriting either the combination of normal eyes/normal wings or purple eyes/vestigial wings together.
In summary, the 1:1 ratio is a result of the close proximity of the genes for eye color and wing size on the same chromosome, leading to linked inheritance and a tendency for these alleles to be inherited together more frequently.
