I'm warning you, though. This isn't vivid prose or beautiful poetry. It's about freaking fruit flies. Haha.

Uncovering the nature of the "Winglessness" Gene in Mutant Drosophila Melanogaster

Introduction

Drosophila melanogaster is more commonly known as the fruit fly. Under normal conditions, d. melanogaster specimens develop functioning wings. However, the males in the P1 generation of my culture displayed a mutation in which they were missing wings completely. This mutation was dubbed "winglessness." This experiment was designed to determine the nature of the gene that caused the trait. After appearing in the males of the P1 generation, it did not appear in any specimens of their progeny, the F1 generation. It was hypothesized that the mutation was the result of an expressed autosomal recessive gene. If the "winglessness" trait was indeed autosomal and recessive, then the expected F2 generation phenotypic ratio was 3 winged males to 1 wingless male to 3 winged females to 1 wingless female.

Materials and Methods

First, two containers were prepared, one each for the progeny of the P1 generation and the progeny of the F1 generation. A blue mixture consisting of food and nutrients for the larvae was placed at the bottom of each container. 6 virgin females and 2 males were placed in the P1 container. All the males displayed the "winglessness" trait, while none of the females did. These P1 adults were removed from the container and placed in an ethanol-filled vial when their progeny, the F1 generation, began to pupate. When the first F1 adults began to emerge, they were removed from the P1 container, anesthetized on a carbon dioxide platform, and then sorted. 5 F1 females and 7 F1 males were placed in the new F1 container. The F1 adults were removed from the container and morgued when their progeny, the F2 generation, began to pupate. The F2 flies were taken out of the container as they reached adulthood and frozen to death in a freezer before being counted and sorted.

Results (My tables won't show up, so you'll have to use your imagination)

Table 1:

Expected Genotypic Ratio for F1 generation

This table shows the expected genotypic ratio of the F1 generation. There should be approximately 1 heterozygous winged male to every 1 heterozygous winged female. All F1s are heterozygous for the winglessness trait, thus, while none display the trait, all are carriers.

Table 2:

Observed Phenotypes of Harvested F1 generation

This table shows the number of F1 flies that were harvested and counted. 13 winged males and 24 winged females were counted. 7 winged males and 5 winged females were harvested and placed in a separate container to breed. No mutated flies were counted in the F1 generation.

Table 3:

Expected F2 Genotypic Ratio

If two heterozygous F1 flies mate, the resulting genotypic ratio of their offspring will be: 1 homozygous winged: 2 heterozygous winged: 1 homozygous wingless

Table 4:

Expected F2 Phenotypic Ratio

If two heterozygous F1 flies mate, the resulting phenotypic ratio of their offspring will be: 3 winged males: 1 wingless male: 3 wingless females: 1 wingless female

Table 5:

Observed Phenotypes of F2 Generation

In the F2 generation, 117 winged males, 24 wingless males, 130 winged females, and 35 wingless females were observed, for a total of 306 flies.

Table 6:

Chi-Square Analysis of F2 Observed Phenotypic Ratios

The determined chi-square value for the data is 7.2. There are 3 degrees of freedom, so the differences between the observed and expected values are significant.

Discussion

In the introduction, I hypothesized that the "winglessness" trait was the result of the expression of an autosomal recessive gene. Table 1 shows that in theory, all the offspring of a homozygous wingless male and a homozygous winged female should be heterozygous winged. Table 2 shows that the experimental results are in agreement with the expected results, as all the F1 offspring were winged.

Table 4 shows that the mating between two heterozygous winged flies would be expected to produce in the F2 generation 3 winged flies to every 1 wingless fly. The results in Table 5 seem to disagree slightly with the expected results as 247 of the F2 flies were winged and 59 were wingless.

Table 6 shows the chi-square analysis of my F2 results. The chi-square value of 7.2, with 3 degrees of freedom, indicates that the difference between the observed and expected values was significant. This means that there is a 5-10% chance that the difference between the expected and observed values was due to random recombination of gametes. Therefore, the hypothesis that the trait of winglessness is due to the expression of an autosomal recessive gene is not supported by this experiment.