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
i. Histone octomer - The histones are positively charged, basic proteins called histones. Histones are rich in basic amino acids like lysines and arginines. Histones are organised to form a unit of eight molecules called an histone octamer.
ii. Nucleosome - The negatively charged DNA is wrapped around the positively charged histone octamer to form the structure called nucleosome. A typical nucleosome contains 200 bp of DNa helix.
iii. Chromatin - The nucleosome are the repeating units and together form chromatin. The nucleosome appear like beads on strings on the chromatin.
The chromatin is packaged to form chromatin fibres that further coil and condense at metaphasic stage of cell division to form chromosome. This involves non-histone proteins for packaging called the No-histone Chromosomal (NHC) proteins.
(b)
| Euchromatin | Heterochromatin |
| Region of the chromatin which is loosely packed. | Region of the chromatin which is densely packed |
| Stains light | Stains dark. |
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.
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