Genetic Inheritance Experiment

Term Paper Title	Genetic Inheritance Experiment
# of Words	1958
# of Pages (250 words per page double spaced)	7.83

Genetic Inheritance Experiment

Andrew Chin
Sect. 0560
Page 2

                                                             ABSTRACT
     The intent of this experiment is to examine the pattern of genetic inheritance.  My test subject is Drosiphila melanogaster, the common fruitfly.  I crossed homozygous wild type females with homozygous recessive males through the F2 generation.  I scored the flies to see if the genes independently assort according to Mendel's Law of Independent Assortment. For my experiment I used two set of flies with two different mutations.  The first set of flies had sepia eyes and apterous wing mutations.  The second set of flies had white eyes and yellow body mutations.  After the flies reproduced through the F2 generation, the first set of the flies gave an approximate 9:3:3:1 ratio that coincides with independent assortment (X = 4.157; .5 > P > .1).  The second set of flies did not give a ratio that could be compared to the 9:3:3:1 ratio (X = 69.869, P P > .1) which coincides with sex-linkage. I concluded that not all genes follow Mendel’s Law of Independent Assortment.

                                                                                                                     Andrew Chin
                                                                                                                     Sect. 0560
                                                                                                                     Page 3

                                                      INTRODUCTION

     According to Mendelian genetics, genes on different chromosomes independently assort.  In Mendel's experiment with the pea plant, the phenotypic ratio of the F2 generation was 9:3:3:1,  rather than an expected 3:1 phenotypic ratio.  The actual outcome implied that the traits were not linked.  Mendel concluded that the traits on the pea plant independently assort.
     In this experiment I chose the common fruit fly to test Mendelian genetics.  Fruit flies are an easy organism to test genetic inheritance.  They  are small and easily maintained, yet large enough for easy handling, observation, and sex determination. They are easily crossed, prolific breeders, and have short generations.  Lastly, the fruit fly has many visible mutations that can be used as genetic markers against the wild-type to trace genetic inheritance (Vliet 1993).
The most common forms of genetic inheritance are independent assortment, autosomal linkage, and sex linkage.  Independent assortment states that genes located on different chromosomes assort independently of each other. If genes are bounded together on the same gene it is said to be linkage.  Genes located on the chromosomes responsible for sex determination (sex chromosomes) are said to be sex linkage; genes located on all other chromosomes (the autosome) show autosomal linkage.  If the observed ratios of the phenotypes of the F2 generation appear to be 9:3:3:1, then it is said to be independent assortment.  If the observed phenotypes appear to be 3:1 without any difference between the males and the females carrying a certain phenotype, then it is said to be autosomal linkage.  If the observed phenotypes appear to be 3:1 with a distinct difference between
                                                                                                                 Andrew Chin
                                                                                                                 Sect. 0560
                                    ...

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