Short Answer Type(a) What do 'Y' and 'B' stand for in 'YAC' and 'BAC' used in Human Genome Project (HGP). Mention their role in the project.
(b) Write the percentage of the total human genome that codes for proteins and the percentage of discovered genes whose functions are known as observed during HGP.
(c) Expand 'SNPs' identified by scientists in HGP.
Long Answer Type(a) Name the stage in the cell cycle where DNA replication occurs.
(b) Explain the mechanism of DNA replication. Highlight the role of enzymes in the process.
(c) Why is DNA replication said to be semiconservative ?
Short Answer TypeDescribe the experiment that helped demonstrate the semi-conservative mode of DNA replication
Long Answer Type(a) How are the following formed and involved in DNA packaging in a nucleus of a cell?
(b) Differentiate between Euchromatin and Heterochromatin
Short Answer TypeA. Name the enzyme that catalyses the transcription of hnRNA.
B. Why does the hnRNA need to undergo changes ? List the changes hnRNA undergoes and where in the cell such changes take place.
Unambiguous, universal and degenerate are some of the terms used for the genetic code. Explain the salient features of each one of them.
A number of passengers were severely burnt beyond recognition during a train accident. Name and describe a modern technique that can help hand over the dead to their relatives.
The technique that can help in the identification of victims is DNA fingerprinting which distinguishes between individuals of same species by using their DNA as sample. The chemical structure of DNA is same in everyone (99.9%) except the order of base pairs, i.e. only 0.1% of DNA makes every individual unique. DNA fingerprinting exploits the highly variable repeating sequences, i.e. VNTRs for profiling. These VNTRs are highly conserved among members of the same species. Technique
This technique has following steps:
(i) DNA Isolation DNA is extracted from the cells in a high speed centrifuge.
(ii) Amplification Many copies of the extracted DNA can be made by the use of polymerase chain reaction.
(iii) Digestion of DNA by restriction endonucleases.
(iv) Separation of DNA fragments by electrophoresis.
(v) Blotting Transfer of separated DNA fragments to synthetic membranes (like nylon or nitrocellulose).
(vi) Hybridisation, with the help of a radio labelled VNTR probe (small segments of DNA which help to detect the presence of a gene in a long DNA sequence). These probes target a specific nucleotide sequence that is complementary to them.
(vii) Autoradiography Detection of hybridised DNA fragments by autoradiography.
The presence of similarities between the victims and their relatives determines their association on the basis of which dead bodies can be identified and handed over to their families.
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