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Fruit Fly

Fruit Fly Investigating Inheritance in Drosophila melanogaster The fruit fly, or the Drosophila melanogaster, was used in this experiment to study patterns of inheritance. It only takes a fruit fly 14 days to develop from an egg to an adult and then 12 hours before they become reproductive, so these factors made the fruit fly a good species to study, because we had enough time to do crosses. We were investigating the patterns of inheritance in the eye color and the wings. The wild type flies had red eyes and full wings, while the mutant phenotype had brown eyes and no wings. We also had to study the sexes of the flies. The male flies had darker abdominal tips and sex combs on both of their forearms. For the results, my group had predicted as follows: X= dominant allele X’= recessive allele This would produce 100% of the dominant phenotype in females. This would produce 100% of the dominant phenotype in males. XX’ x XY X-linked Recessive This would produce 100% of the dominant phenotype in females with 50% carrying the recessive trait. This would produce 50% of the dominant phenotype in males and the other 50% of males would express the recessive trait. A= dominant allele a= recessive allele This will result in a 100% dominant phenotype. We had received 2 cultured bottles and added a few grains of yeast and some cool water. We had received wild type flies to sex and had to set up crosses with them. After anaesthetic that we used to put them to sleep, we emptied them onto a piece of white paper and viewed them under a dissecting microscope one by one to determine their individual sexes. We then had set up a vial with 5 wild type males and one female, checking the vial periodically for any change. Our next step was to make up a vial of mutants. Once both vial were set up, all we had to do is wait for an appearance of eggs or larvae. By the completion of week 2, we started to see larvae, which meant that we had to take the initial flies out so not to disturb our counts. We had discarded the females and put the wild type and mutant males into new vials. The bottles were checked periodically for the formation of females. We then took the second generation and crossed the mutant females with the wild type males and the wild type females with the mutant males. After seeing larvae a week later, we discarded those adult flies. We then counted and recorded our results over the couple of weeks. The dates that we had counted were October 16, 18, 19, 20, 26, 27, and 30. The cross between the mutant males and the wild type females was predicted (out of 100 flies) that it would result in 50 wild type females and 50 wild type males. We had observed a yield of 55 wild type females and 44 wild type males. The cross between the wild type males and the mutant females was predicted to produce 50 mutant males and 50 wild type females. We had come up with 35 wild type females, 21 wild type males, 4 mutant females, and 40 mutant males. Our results from the first cross had indicated that red eyes on the flies were dominant to brown eyes and that presence of wings is dominant to the absence of wings. We also had discovered that the traits were autosomally inherited, though the sexes of the flies varied. There was a large variation in the second cross between the predicted results and the observed results. We were not able to understand the pattern of inheritance in this cross. Our prediction of the dominant trait being red eyes and with wings was correct, but our mode of inheritance was wrong. We were not able to prove or disprove the mode of inheritance. We also had problems with our second cross. We may have placed the wild type flies or the mutant flies in the wrong vial to produce the wrong outcome. We also could have had a mistake in counting. We also could have left a female in the container that was not really a virgin. This could have produced our wrong results. If possible, we should have set up two separate sets of flies. Although it would have been extra time, it would have provided a better outcome because we would have a great sample. Bibliography:

Word Count: 760