Background & Purpose
Endomitosis is a variant of the cell cycle that leads to the production of up to a thousand copies of the genome. During this process, the cell does not divide but the chromosomes increase in size as the number of copies of genes increases. The purpose of this lab was to investigate endomitosis in the salivary glands of Drosophila virilis larvae. It was hypothesized that endomitosis also occurs in the salivary glands of Drosophila virilis. This hypothesis was formulated based on the fact that endomitosis has been reported to occur in Drosophila melanogaster, which is closely related to Drosophila virilis.
Results
The images of the human cells and salivary glands of Drosophila virilis as observed under the compound microscope are shown in the appendix in figures 1 and 2.
Discussion
It was hypothesized that endomitosis took place in the salivary glands of Drosophila virilis. The findings of the experiment showed the presence of polytene chromosomes, which were only produced in endomitosis, in the salivary glands of the larvae of Drosophila virilis as shown in figure 2. The polytene chromosomes were distinctive from the mitotic chromosomes in human cells (shown in figure 1). Some of the major differences were the sizes of the two chromosomes. Figure 1 showed small mitotic chromosomes in human cells while figure 2 showed significantly big polytene chromosomes in the salivary glands of Drosophila virilis. Another major difference was the presence of several polytene chromosome arms in Drosophila virilis whereas the human mitotic chromosome only had four distinctive arms. However, the chromocenter of the polytene chromosome was not easily distinguishable. Therefore, the findings of this experiment supported the hypothesis that endomitosis occurred in the salivary glands of Drosophila virilis larvae.
Appendix
Figures
