Part B-Dec 2016

CSIR-UGC National Eligibility Test (NET) for Junior Research Fellowship and Lecturer-ship

Some Important Questions Collected from the Memory of Students and Probable Questions and Answers

Previous Year Questions & Answers –Part B. Dec 2016

1. RNA editing, a post-transcriptional process, is achieved with the help of guide RNA (g-RNA). Which one of the following statements about the process is NOT true ?
1. g-RNA dependent RNA editing happens in the kinetoplast DNA
2. g-RNA is involved in chemical modification of t-RNA
3. This process involves insertion or deletion of uridines
4. Sequences edited once may be re-edited using a second g-RNA
Ans:- 2
Expln:- A kinetoplast DNA is a network of circular DNA inside a large mitochondrion that contains many copies of the mitochondrial genomes. Mitochondrial DNA of some protists like trypanosoma is example for kinetoplast DNA. Guiding RNA never modify the t-RNA.
2. Telomerase, a RNA-protein complex which completes the replication of telomeres during DNA synthesis, is a specialized
1. RNA dependent DNA polymerase
2. DNA dependent DNA polymerase
3. DNA dependent RNA polymerase
4. RNA dependent RNA polymerase
Ans:- 1
Expln:- The linear chromosomes of eukaryotes face special difficulties in replicating the terminal ends called telomeres. Although the leading strand can theoretically be replicated to the very end of its template, the
lagging strand cannot. There is no sufficient place to synthesize a primer that would allow the daughter strand to be completed. Hence the daughter strand will be shorter than the parental strand. Removal of the last RNA primer would leave a short gap that makes the daughter strand even shorter. The telomeres avoid this problems by adding repeated six-nucleotide (TTAGGG) sequence. Human telomeres contain thousands of such repeats.
Telomerase is a ribonucleprotein complex containing a small RNA that serves as a template for addition of new nucleotide repeat. This RNA carries the sequence complementary to the TTAGGG sequence (in humans). Thus, the enzyme telomerase has two important properties:
It is a reverse transcriptase, i.e. it uses an RNA template for DNA synthesis, and
It carries the built in RNA template in its structure.
3. Consider a short double-stranded linear DNA molecule of 10 complete turns with 10.5 bp/turn. The ends of the DNA molecule are sealed together to make a relaxed circle. This relaxed circle will have a linking number of
1. 105               2. 20.5
3. 10.0               4. 10.5
Ans:- 3
Expln:- In the case of relaxed DNA there is no writhe and the linking number, Lk is equal to the twist, Tw. As number of turns is equal to 10 so the linking number will be 10. Lk = Tw + Wr

In the above signalling cascade, which one of the following  molecules is denoted by ‘B’ ?

1.STAT 5                  2.SMAD 6

3. GSK3 β               4. SMAD 4

Ans:- 4


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