Fly Report - I. Abstract Drosophila is a model organism for...

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I. Abstract Drosophila is a model organism for studying genetic inheritance because many of its genetic mutations lead to phenotypes that can be easily seen with a dissecting microscope. When a true breeding mutant strain is found, geneticists can determine on which chromosomes the mutations occurred by making crosses with known true breeding stocks. The unknown D. melanogaster mutant strain named Kiryuu in this report has three phenotypic characteristics distinguishing it from the wild type strain. Kiryuu has an unusually dark body ( charcoal = ch) , white eyes ( white = w) , and its longitudinal wing veins LIV and LV are shortened ( midget = mi) ; they do not reach the edge of the wing like the veins do in a wild-type fly. After making several crosses between Kiryuu and true breeding stocks, and generating an F2 generation, a brown eye color emerged, which was then called burnt (bu) . The 1A and 1B crosses elucidated the mode of inheritance for all of these genes. Two genes were in control of eye color; the white eye gene only arises in 1A F1 generation males and is not present in the 1B F2 generation females. This means that white is recessive and sex linked. The burnt mutation is found to be autosomal and recessive because it is not present in any F1 generation flies and present in the 1B F2 generation females when white was not, also alluding to the fact that white is epistatic to burnt . Neither the charcoal or midget genes were present in the F1 generation and both were present in all of the F2 generation flies, meaning that these two mutations are autosomal and recessive. The male parent back cross and female parent back cross were used to map the 2 nd chromosome while the marker stock 4 cross was used to map the X chromosome. The following maps were created: Chromosome 2: X Chromosome: II. 1A and 1B Crosses The 1A and 1B crosses were done to determine the number of genes affecting each mutant phenotype, and to determine whether the genes were: dominant or recessive, and autosomal or sex linked. In the 1A and 1B 1 98.92 71.06 54.8 43.21 6.17 bu L Bl ch mi 53.12 13.7 0 f cv w
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crosses, true breeding wild type flies were mated to the mutant strain Kiryuu . The 1A cross was between Kiryuu females and wild type males, while the 1B cross was between wild type females and Kiryuu males. A distinction was made between which parent was the unknown because homologs in male Drosophila never recombine. After the 1A and 1B crosses eclosed, the 1A F1 females and males were mated and the 1B F1 females and males were mated. The F2 generations were used to determine the number of genes controlling each trait and whether they were linked or not. The Kiryuu mutant strain of D. melanogaster differs phenotypically from the wild type strain in three obvious ways. Wild type flies have red eyes, tan bodies, and fully veined wings (longitudinal veins LI – LV, and two cross veins between LIII-LIV and LIV-LV). Kiryuu flies have white eyes, shortened longitudinal veins LIV
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This note was uploaded on 11/05/2009 for the course BIO 2810 taught by Professor Fox/nero during the Spring '07 term at Cornell University (Engineering School).

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Fly Report - I. Abstract Drosophila is a model organism for...

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