Fruit Fly Chi Square and Intro

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  • Topic: Drosophila melanogaster, Insect, Genetics
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  • Published : April 29, 2012
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Drosophila melanogaster: Mutant Fruit Flies
Jessica E. Phillips
Genetics 3301
April 13, 2012
Introduction:
Drosophila melanogaster better known as the fruit fly can be found near rotting fruits, vegetables, or anywhere where there is food that has rotted and or fermented. (Potter, 2010) D. melanogaster has four different stages in its life cycle. The first stage of D. melanogaster is the egg which can last for about one day; then turns into a larva. The larva stage last for about 7-8 days. Once the larva mature it will molt twice this period is called an instar. (Flagg, 1979) Instar means that the larva will shed a cuticle, mouth hooks, and spiracles and the period in which it goes through this growth phase of molting. D. melanogaster will go through 3 instars before reaching the pupa stage. (Flagg, 1979) The pupa stage will last for about 6 days after which the adult will eclose. During the pupa stage the pupa will darken and the eyes as well as the wings will appear visible through the casing. Gregor Mendel created 3 principles as it relates to the laws of genetics. The 3 principles of Mendel’s laws of genetics are the law of dominance, the law of segregation and the law of independent assortment. The law of dominance stated that in a heterozygous condition, the dominant allele will dominate over another allele. This means that the dominant trait or phenotype will be present. The law of segregation states that for any trait or phenotype, the parent alleles will separate and only one allele from each parent will pass to the offspring. (O’Neil, 2011) The law of independent assortment states that different pairs of alleles are passed to each other independently. (O’Neil, 2011) Because of Mendel’s laws, D. melanogaster, is the organism often studied for genetics research. Some of the reason for studying the flies genetically is because they are small and easy to grow in a lab setting. They have a 2 week life cycle and a new generation can be produced rapidly. (Kimball, 2011) Females can lay about 500 eggs within in her life span which give large populations that can be used for statistical analysis. (Hansen & Ferris, 1929) The embryo of the fruit fly grows outside the body which makes it easy to study the life cycle. (Kimball, 2011) Mutations can also be targeted to specific genes easily. (Kimball, 2011)

The purpose of this experiment is to observe the 3 basic principles of Mendelian genetics in the Drosophila melanogaster. The life cycle of the fruit fly will be examined and mutant crosses will be set up between flies with different genotypes which in turn exhibit different phenotypes. Dihybrid crosses will be conducted using the same pattern as Mendel and predict that the flies should follow the same pattern from the parental generation, to the F1 generation also known as the parents, and last but not least to the F2 generation using Mendel’s laws. From the data gathered, chi square analysis will be conducted to determine the phenotype and genotype of the parent generation and so on. Based on understanding Mendelian genetics and how sex linked traits work, the flies will exhibit autosomal sexlinked traits that will code for eye color and change in body/wings. Procedure:

Materials:
The materials needed for this lab were clear sterilized plastic vials that are used for growing the flies. Each vial will have a plastic foam cover to allow for the flies to get air but stop them from flying out. Formula 4-24 was used as a growing medium inside the vials. Food for D. melanogaster was yeast. Other materials needed for the fruit fly experiment was a fine sorting brush, white note cards, and microscope which will be used to observe the flies. Methods:

Two vials of Drosophila melanogaster was obtained from the lab instructor on February 28, 2012 to be grown and reproduced in the lab for one week. The vial contained the F1 generations of the fruit fly. Vial #1 was dated for 2-17-12 and Vial #2 was...
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