Genetics - Analysis and Principles
Quiz 11 :
The double helix is made up of two DNA (deoxyribonucleic acid) stands, and nucleotides for the individual building blocks of each strand. The nucleotides comprise one of four bases namely adenine, thymine, guanine, and cytosine. The base stacking and hydrogen bonding between the bases are responsible for holding the double-stranded structure together. The key structural feature of the DNA molecule that underlies its ability to be faithfully replicated is the AT/GC rule. According to the AT/GC rule adenine hydrogen bonds with thymine, and guanine hydrogen bonds with cytosine. This forms the basis for complementarity of the base sequences in the double-stranded DNA.
Meselson and Stahl experiments explain the semi-conservative method of DNA replication. It states that only one strand is inherited from the parent generation and the other strand is newly synthesized. A. • If Meselson and Stahl experiment were carried out for four generations, following would be the result: 7/8 light, 1/8 half-heavy. • If Meselson and Stahl experiment were carried out for five generations, following would be the result: 15/16 light, 1/16 half-heavy. B.• If Meselson and Stahl experiment following three generations in case the mechanism of DNA replication was dispersive the entire DNA double helices will have 1/8 heavy. C.• The CsCl gradient splits molecules based on their densities. • 15N-containing have higher density than 14N-containing compounds. • The bases of DNA have nitrogen. • In case the bases have only 15N then the DNA would be heavy and would sediment at a greater density. In case the bases have only 14N then the DNA would be light and would sediment at a lower density. In case the bases in one DNA strand contain 15N and the bases in the other strand contain 14N, then it would be half-heavy and would sediment at an intermediary density.
There are a lot of possibilities. However, the underlying principle would be chemical recognition. There must be stringent and specific conditions on the basis of which two structures identify each other. Like DNA (deoxyribose nucleic acid) there are several molecules are involved in the faith full copy mechanism, which include Viral RNA (ribonucleic acid). When the virus enters into his host their genome integrates into the host genome, than it replicated along with host DNA and gives the exact replicas of viral RNA. These RNA are expressed and produce assembly proteins. Upon the viral RNA and proteins are assembles and synthesizes new viral particles, that are exactly similar to their parent virus. This phenomenon is called as self-replication.