Drosophila melanogaster - Drosophila melanogaster Katherine...

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Drosophila melanogaster Katherine Hankins April 24, 2008 Genetics Laboratory Section 06
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Introduction The purpose of the Drosophila melanogaster , or common fruit fly, experiment is the study of Mendelian genetics and the laws of inheritance. The completion of the dihybrid crosses between white eyed and ebony bodied males and females holds the possibility of proving the laws of inheritance. There are two theories: the first based on a dihybrid cross between a female white eye and beige bodied fly with a male red eye and ebony bodied fly predicts non sex-linked traits and a 9:3:3:1 ratio in the F2 offspring. The second hypothesis predicts that a reciprocal dihybrid cross between a female white eye and ebony bodied fly and a male red eye and beige bodied fly will show sex-linked trait tendencies in the F2 offspring resulting in a ratio of 6:2:6:2. The experiment begins with two stock vials of the parental (P1) D. melanogaster flies. First, the males and virgin females must be isolated from the two different vials and using an already prepared culture vial, the virgin females (three to five) are introduced with males from the opposite vial from which the females originated (Mendelian Crosses Using Drosophila 17-18). After the mating P1 produce F1 progeny, which are then allowed to mate with other F1 offspring, the F2 progeny should demonstrate the predicted results in either the first or reciprocal cross. These predictions are based on the following laws of inheritance: the principle of segregation and the principle of independent assortment (the first and second laws respectively). The principle of segregation states that a trait is controlled by a pair of alleles which separate and segregate into the gametes during meiosis. The principle of independent assortment follows by stating that during gamete formation, the members of one pair of genes segregate independently of all other pairs of genes (Mendelian Genetics Handout 1).
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In Mendel’s experiments which produced the laws of inheritance, he used the garden pea ( Pissum sativum ) for the same reasons that the fruit fly is used in this experiment: they are inexpensive, reproduce quickly, and have distinct traits (Mendelian Genetics PPT 14). The other benefits specific to using D. melanogaster include: small size, 10 day new generation time, the female lays 400-500 eggs, they have a small and already mapped genome with 4 large chromosomes, and there are many available mutations (Intro to the Drosophila melanogaster PPT 3). The distinguishing traits for the different sexes of D. melanogaster are: size (female larger than male), abdomen shape (the female abdomen is distended and pointed while the male abdomen is round and cylindrical, banding patterns (the female dorsal rear portion has defined alternating light and dark bands while the male dorsal rear portion has fused bands), the best method of differentiation is sex combs, which are only on the males as seen in figure 3 (Intro to the Drosophila melanogaster
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This note was uploaded on 05/03/2008 for the course BIO 2322 taught by Professor Spotswood during the Spring '08 term at The University of Texas at San Antonio- San Antonio.

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Drosophila melanogaster - Drosophila melanogaster Katherine...

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