Part B-June 2016

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

Part B


This time CSIR does not allow candidates to carry questions with them. We have collected maximum questions from our candidates (memory based).

1.Which of the following is NOT true for cholesterol metabolism?
1.   HMG-CoA reductase is the key regulator of cholesterol biosynthesis.
2.   Biosynthesis takes place in the cytoplasm.
3.   Reduction reactions use NADH as cofactor.
4.   Cholesterol is transported by LDL in plasma.
Ans: 3
Reduction of HMG-CoA to mevalonate during cholesterol metabolism is mediated by the enzyme HMG-CoA reductase and use NADPH as cofactor and not NADH. Similarly, reduction reaction of farnesyl pyrophosphate to squalene also use NADPH.[For more details: Refer Biochemistry in Simple Instant Notes].
2. Entry of enveloped viruses into its host cells is mediated by:
1. Only endocytosis
Both endocytosis and phagocytosis
3. Both endocytosis and membrane fusion
4. Only pinocytosis
Enveloped viruses enter the host cell by fusing either with the plasma membrane or with the endosomal membrane following endocytosis. Non enveloped viruses generally either form a pore in the cell membrane to deliver the viral genome into the cytoplasm or they disrupt the endosomal membrane after endocytosis.[For more details: Refer host parasite interaction in Simple Instant Notes].
3. Lateral diffusion of proteins in membrane can be followed and diffusion rate calculated by
1.  Atomic force microscopy
2.  Scanning electron microscopy
3.   Transmission electron microscopy
4.   FRAP
Ans:- 4
Expln:- Fluorescence recovery after photobleaching (FRAP) denotes an optical technique capable of quantifying the two dimensional lateral diffusion of a molecularly thin film containing fluorescently labeled probes, or to examine single cells. This technique is very useful in biological studies of cell membrane diffusion and protein binding. FRAP can also be used to monitor proteins outside the membrane. After the protein of interest is made fluorescent [generally by green fluorescent protein (GFP)], a confocal microscope is used to photobleach and monitor a region of the cytoplasm, mitotic spindle, nucleus etc.[For more details: Refer Lipid bilayer and membrane protein diffusion in Simple Instant Notes].
4. Histone deaceytalase (HDAC) catalyses the removel of acetyl group from N-terminal of histones. Which amino acid of histone is involved in this process?
1.   Lysine
2.   Arginine
3.   Asparagine
4.   Histidine
Ans:- 4
Expln:- The amount of binding between DNA and histones can be altered by a process called acetylation. HAT (Histone acetyl transferases) enzymes transfer a two carbon acetyl group to the ends of particular amino acids in the histone proteins. The addition of the acetyl group to positively charged amino acids such as lysine removes the charge and reduces the overall affinity of the histones for the negatively charged DNA. In this configuration, the DNA is more accessible for transcription factors and transcription is increased. Histones deacetylase (HDAC) deacetylate histones.
When the histones are deacetylated, the positive charges are restored and the DNA binds to it more tightly. Deacetylation leads to a repression of transcription because the necessary transcription factors, regulatory factors, and RNA polymerase complex are unable to gain access to the DNA.[For more details: Refer Role of Chromatin in Regulating Gene Expression in Simple Instant Notes].
5. RNA interference is mediated by both siRNA and miRNA. Which one of the following statement about them is NOT true?
1.   Both siRNA and miRNA are processed by DICER.
2.   Both siRNA and miRNA usually guide silencing of the same genetic loci from which they originate.
3.   miRNA is a natural molecule while siRNA is either natural or a synthetic one.
4.   miRNA, but not siRNA is processed by Drosha.
Ans:- 2
Expln:- Almost all siRNAs (regardless of their viral or other origin) silence the same locus from which they were derived. On the other hand, most miRNAs do not silence their own loci, but other genes instead.[For more questions and answers refer Simple Instant Notes].

More Questions & Answers Refer Simple Instant Notes