Question

In fruit flies, Red-Eyes (R_) are Dominant to Purple-Eyes (rr) and Normal Wings (VG_) are Dominant to Vestigial Wings (vgvg). A True Breeding Red-Eyed fly with Vestigial Wings is crossed to a True Breeding Purple-Eyed fly with Normal Wings. The F1 progeny are then used in a Test cross. The results of the Test Cross show that 1/2 of the offspring have Red-Eyes and Vestigial Wings. The other 1/2 of the progeny have Purple-Eyes and Normal Wings. What do these results suggest about these genes

Answer 1

The test cross findings, showing a 1:1 phenotypic ratio of Red-Eyes with Vestigial Wings to Purple-Eyes with Normal Wings in the F1 progeny, suggest that the genes for these traits in fruit flies assort independently according to Mendelian genetics.

Step-by-step explanation:

The question relates to Mendelian genetics and, specifically, the inheritance of two traits in fruit flies (Drosophila melanogaster): eye color and wing type. Eye color in fruit flies is an X-linked trait, and because of this, male offspring only inherit one allele (hemizygous), while females have two alleles. In the given scenario, Red-Eyes (R_) are dominant to Purple-Eyes (rr) and Normal Wings (VG_) are dominant to Vestigial Wings (vgvg). When a True Breeding Red-Eyed fly with Vestigial Wings is crossed with a True Breeding Purple-Eyed fly with Normal Wings, the F1 progeny are expected to be heterozygous for both traits. The results from the Test Cross suggest that the genes for eye color and wing type are assorted independently since each trait's inheritance does not affect the other's, which leads to the observed 1:1 phenotypic ratio in the offspring, where half have Red-Eyes and Vestigial Wings and the other half have Purple-Eyes and Normal Wings.

Answer 2

The results suggest that the genes for eye color (Red-Eyes and Purple-Eyes) and wing type (Normal Wings and Vestigial Wings) assort independently, indicating the principles of Mendelian inheritance.

When a True Breeding Red-Eyed fly with Vestigial Wings (R_Vgvg) is crossed with a True Breeding Purple-Eyed fly with Normal Wings (rrVGVG), the F1 progeny will be heterozygous for both traits (RrVgvg). This is due to the dominance of Red-Eyes and Normal Wings. In a Test cross using these F1 flies, if the genes assort independently, you would expect a 1:1:1:1 ratio of phenotypes (Red-Eyes/Normal Wings, Red-Eyes/Vestigial Wings, Purple-Eyes/Normal Wings, Purple-Eyes/Vestigial Wings).

The observed result of 1/2 having Red-Eyes and Vestigial Wings and the other 1/2 having Purple-Eyes and Normal Wings aligns with this expected ratio. It indicates that the genes for eye color and wing type are segregating independently during gamete formation, following Mendel's Law of Independent Assortment.

In conclusion, the 1:1 ratio of phenotypes in the Test cross supports the hypothesis that the genes for eye color and wing type are located on different chromosomes or are sufficiently far apart on the same chromosome to assort independently. This observation reflects the principles of Mendelian inheritance and independent assortment of genes.