Salivary Gland Chromosome Preparation
Introduction:
The mastery of the technique of preparing salivary gland chromosomes allows me to study many intriguing aspects of gene function during the course of larval development. The significance of this experiment is to utilize and study salivary gland chromosomes for cytological examination, and to compare the relative size of my salivary gland chromosome with human metaphase chromosomes.
In my particular larvae, endomitosis has occurred, in which the chromosome duplicates without cell division, resulting in polytene chromosomes.
Material and Method:
The preparation and extraction procedure was in accordance to the Biology Department. 2014. Laboratory Manual for Introductory Genetics. Ottawa: Carleton University. I obtained desirable data of chromosome through the observation of internal larval structures of third instar D. melanogaster by using a given slide from my lab coordinator.
Results:
Figure 1 depicts polytene chromosome of D. melanogaster consisting of two visible chromosomal tips, which join one another in a large unbanded mass. There are irregularly spaced bands with different bandwidths present, varying in thickness and distribution along the length of each chromosome. There are no visible puffs or a visible nucleus. My salivary gland chromosome is much larger in comparison to the human metaphase chromosomes, which are discontinuous stick-like structures.
Discussion:
My hypothesis was correct; the polytene chromosomes arise due to endomitosis (Biology Department, 2014). Factors of polytene chromosomes were detected; big, light, and dark banding patterns. All of the homologous pair of chromosomes is connected to chromo centers (Baudisch, W. 1977). The lack of mitosis causes successive doubling in the original, permanently synapsed homologous chromosomes, which results in irregular bandwidths and puffs (Alberts et al., 1994). In comparison, D. melanogaster chromosome is much larger than the...