Photosynthesis Lab Hypothesis
Introduction
A chromosome is a minuscule threadlike part of the nucleus and a structured DNA in the form of genes carrying hereditary information (Bridges, 1938). Endomitosis is the process of mitosis of chromosomes without undergoing nuclear or cellular division to increase cell volume. This results in a single nucleus having many copies of a single chromosome (Painter & Reindorp, 1940). In this experiment, Drosophila melanogaster is reared in specific conditions and its salivary gland extracted to study endomitosis. I hypothesize that I will see endomitosis in the salivary gland chromosome of third instar larval D. melanogaster. My prediction to test my hypothesis is that polytene chromosomes will be formed if endomitosis occurs.
Materials …show more content…
melanogaster with chromosome arms labelled (approximately)
From figure 2, I can observe that the bands of the chromosome are irregularly spaced with varying band widths I did not see any puffs. I observed that the chromosomes of D. melanogaster were much larger in size and easier to study than human chromosomes.
Discussion
I observed that polytene chromosomes had formed just like my prediction. This result supports my hypothesis that endomitosis has occurred. I observed that polytene chromosomes were big, light and had dark banding patterns with all homologous pairs of chromosomes connected to chromocentre similar to Baudisch 's observation in his 1977 paper. The disadvantage of the method used was that the extraction process was very hard and without lots of practise is a not practical method for fast good results. The biological significance of endomitosis is not fully and properly understood but scientists have hypothesized the following factors for its occurrence - cell size and differentiation, embryonic development, and as a response to stress. When I compared the metaphase chromosomes of D. melanogaster and human, the chromosomes of D. melanogaster were huge and easy to study compared to that of the human. However, the chromosome of human which is very small in size to that of D. melanogaster, is the one that is considered as normal size for a
A chromosome is a minuscule threadlike part of the nucleus and a structured DNA in the form of genes carrying hereditary information (Bridges, 1938). Endomitosis is the process of mitosis of chromosomes without undergoing nuclear or cellular division to increase cell volume. This results in a single nucleus having many copies of a single chromosome (Painter & Reindorp, 1940). In this experiment, Drosophila melanogaster is reared in specific conditions and its salivary gland extracted to study endomitosis. I hypothesize that I will see endomitosis in the salivary gland chromosome of third instar larval D. melanogaster. My prediction to test my hypothesis is that polytene chromosomes will be formed if endomitosis occurs.
Materials …show more content…
melanogaster with chromosome arms labelled (approximately)
From figure 2, I can observe that the bands of the chromosome are irregularly spaced with varying band widths I did not see any puffs. I observed that the chromosomes of D. melanogaster were much larger in size and easier to study than human chromosomes.
Discussion
I observed that polytene chromosomes had formed just like my prediction. This result supports my hypothesis that endomitosis has occurred. I observed that polytene chromosomes were big, light and had dark banding patterns with all homologous pairs of chromosomes connected to chromocentre similar to Baudisch 's observation in his 1977 paper. The disadvantage of the method used was that the extraction process was very hard and without lots of practise is a not practical method for fast good results. The biological significance of endomitosis is not fully and properly understood but scientists have hypothesized the following factors for its occurrence - cell size and differentiation, embryonic development, and as a response to stress. When I compared the metaphase chromosomes of D. melanogaster and human, the chromosomes of D. melanogaster were huge and easy to study compared to that of the human. However, the chromosome of human which is very small in size to that of D. melanogaster, is the one that is considered as normal size for a