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©This page is Copyright Justin Hutchings, 2001. Do not duplicate without express permission from the author.
Genetic Study of the Yellow Body Mutation in a Small Community of Drosophila
Drosophila Melanogaster
In order to understand the nature of this experiment one must first understand the subject of the testing. The Drosophila Melanogaster, commonly refered to as the fruit fly, was our test subject. The Drosophila are about 3mm long and in nature eat rotting fruit, hence the common name, the fruit fly.(3) They have been in use for genetic research for many years because of their short lifespan, large number of offspring, and because of the fact that they require little maintainence like food, water, or space. In addition much is known about the Drosophila. For instance, the Drosophila genome project is completed and the world can reference the information from that project1.(2)
The life cycle of the Drosophila is of the same type as any other diptera (an order of the insect kingdom). The life cycle2 takes about 14 days and goes as follows: A fertilized egg is laid by an adult female. The egg is laid onto a food surface life fruit, or a scientific media. The egg then changes into a white larva. This larva is commonly known as a maggot. These larva are characterzed by an extremly large appetite and rapid growth. The larva will molt twice within the larva period and the time between molts are called instars. The third instar ends when the outer skin darkens and hardens this forms the pupal case. Throughout next stage, the pupal stage, the larval tissue breaks down and a new, winged adult is formed. The adult then breaks from the pupal shell. Its wings are not expanded upon exiting the pupal shell, so the fly must wait for them to expand, dry and stiffen before they can be used for flight. The final stage is the adult stage where mating takes place. The female stores sperm after mating and releases the sperm as eggs are produced. A healthy female can produce as many as 1000 eggs. Males and females may mate more than once. Some of the stored sperm in the female might be displaced by the sperm of the most recent mating.(1)
The mutation I am studying is that of the gene yellow3, or gene y. This gene is mapped by the Fly Base as 1A8--B1. It is expressed in the embryo (Keilin's organ, anal plate, epidermis, microchaetae and 5 others), pupa (epidermis), and adult (cuticle).(4) 
The gene annotation for gene y.
The reason we study this gene is so that some day in the future, we can test gene therapy to see if we can suppress this and other mutant genes. This is all in the hopes that one day human genetic problems like a tendency to get a certain cancer, can be treated.
Genetics
| Now that we have reviewed the flies we will review the science of genetics. Genetics was developed almost inadvertently by a monk in Hungary by the name of Gregor Mendel (1823-1844)4, who learned everything he could about the pea plants in his garden. He crossed certain ones and noted the results. He died confident that he had discovered everything there is to know about pea plants. What he did not know was that the properties he discovered about pea plants hold true in all life because of similar genetic material. |  |
| The Punnett square is one of the most useful tools in Mendelian Genetics. A Punnett square is displayed at right. The Punnett square is used to predict offspring in certain crosses. The cross at right is that of two hetrozygous parents. It reveals that the offspring should be 25% homozygous dominant (where dominance is represented by a capital letter and recessive is a lower case letter), 50% hetrozygous and 25% homozygous recessive. The Chi-square is a test to determine,wether or not there is a high probability that the observed results confor to some predictable oputcome based on an underlying biological phenomenon. So, in short results from an experiment have an exceptable margin of error.(1) Hypothesis |
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1For access to the genome project for Drosophila click here.
2For a photographic version illustrating the journey from egg to fly click here.
3For more information on the yellow body gene that is not nessasary here, click here.
4To see a quick biography about Gregor Mendel, click here.
