December 4, 2012
Genetics is a topic that has been studied for hundreds of years. One of the most notable geneticists was Gregor Mendel. Mendel studied basic inheritance patterns and gene expression using pea plants. Mendel determined that the offspring of two parents contains one gene from each parent (McKusick 1983). However, since Mendels discoveries in genetics, other scientists have found exceptions to Mendels rules, and have termed these exceptions Non-Mendelian Genetics. One type of Non-Mendelian genetic inheritance pattern is X-Linked traits (Brooker 1999). Drosophila, or fruit flies, was chosen for the study of X-Linked traits for multiple reasons. Fruit flies are small insects approximately 3mm long, and thus use minimal space when compared to other species. The diet of fruit flies is simple and does not require extraneous foods or materials (Ullrey 2011). Additionally, the life cycle of fruit flies is quite short, lasting approximately 26 days for a female and approximately 33 days for a male (Ullrey 20111). Lifecycles of flies may be altered based on environment or certain genetic mutations. From egg to adult takes approximately 10 days at room temperature (25°C) (Ullrey 2011). The short life span of fruit flies makes them an ideal subject for the study of genetics, as multiple generations can be studied in a short period of time. The life cycle of a fruit fly starts when an impregnated female fruit fly lays an egg. Fruit flies lay only one egg at a time. The egg hatches in 22 hours, and the larvae eats and grows for four days. The larvae go through three larva stages before entering the pupa stage. In the pupa stage, the pupal case forms, darkens and hardens for 4-6 days. Finally, the pupa closes into the adult stage. Male fruit flies have a smaller body with a rounded black tip at the end of their body. Females, on the other hand, have a pointed abdomen and are often lighter than males (Ullrey 2011). The purpose of the experiment was to determine the type of inheritance within the fruit flies. Whether the fruit flies carry a dominant or recessive trait and how it’s applied in a monohybrid analysis and dyhybrid cross. This experiment was done in two parts from two separate weeks. There are also lab table results and a whole class result of the experiment. Hypothesis
When the wild type and mutant type flies reproduce to make the F2 generation there will be more wild types than mutant types. This is because wild type is dominant. For a monohybrid analysis there will be a 3:1 ratio, 3 being wild type and 1 being mutant. For a dyhybrid cross there will be a 9:3:3:1 ratio of fruit flies. 9 being wild type, 3 being wild-type eyes and no wings, 3 being mutant eyes and wings, and 1 being mutant eyes with no wings. Null Hypothesis
When the wild type and mutant type flies reproduce to make the F2 generation there won’t be a difference between the two. The wild type won’t be dominant. For a monohybrid cross there won’t be a 3:1 ratio, wild type to mutant. There will be half wild type and half mutant. For a dyhybrid cross there won’t be a 9:3:3:1 ratio, there will all be a 4:4:4:4 ratio.
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