Cross I Lab Report

The purpose of this experiment was to determine if two selected traits of Drosophila melanogaster, dumpy wings and sepia eyes, follow Mendel’s Laws of Inheritance through the F2 generation. Materials and Methods In week one, two crosses were set up. Dumpy females were crossed with sepia males, while dumpy males were crossed with sepia females. The dumpy phenotype consisted of shorter, smaller wings while the sepia phenotype consisted of brown eye color. For these crosses, all females were virgins. These crosses were the P1 generation.

These crosses were then incubated until week two. ?In week two, the parents were removed and disposed of. The eggs and larve were left to continue the cross. The crosses were left to continue to incubate until the following week. ?In week three, the flies emerging from each cross of the P1 generation were counted, separated into male and female, and then further separated into phenotype. This marked the completion of the P1 generation. The F1 crosses were then begun. They were set up in there different ways.

In Cross A, F1 females were paired with F1 males. In cross B, F1 virgin females were paired with dumpy sepia males. In the last cross, Cross C, dumpy sepia virgin females were crossed with F1 males. In crosses B and C, only virgin females were used. The virgin females used were obtained from the P1 crosses. Dumpy sepia virgins were acquired from a source outside the experiment. The crosses were left to incubate until week four. ?Week four proceeded much like week two, with the parents being removed and discarded.

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The eggs and larve were left undisturbed to continue the cross. They were allowed to incubate until the final week, week five. ?In the final week, week five, the flies emerging from the F2 crosses and the backcross were counted, separated into male and female, and then further separated into phenotype just as week three. The crosses were then disposed of. Results F1 x F1 Cross Raw Data Wt Dp Se dpse M F M F M F M F Table 1 26 19 8 9 7 11 2 4 Table 2 Table 3 39 43 7 10 16 25 1 3 Table 4 34 56 17 13 16 16 3 6 Total 99 118 32 32 39 52 6 13

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