CSIR UGC JRF NET Life Sciences JUNE 2015 Solved Questions and Answers

1. When bacteria growing at 20^o C are warmed at 37^o C, they are most likely to synthesize membrane lipids with more
a. Short chain saturated fatty acids
b. Short chain unsaturated fatty acids
c. Long chain saturated fatty acids
d. Long chain unsaturated fatty acids

2. Which one of the following compounds is generally translocated in the phloem?
a. Sucrose
b. D-Glucose
c. D-Mannose
d. D-Fructose

3. Given below are some statements about prokaryotic and eukaryotic mobile genetic elements or transposons.
A. Most mobile genetic elements in bacteria transpose via an RNA intermediate.
B. Most mobile genetic elements in bacteria are DNA
C. Mobile genetic elements in eukaryotes are only retrotransposons.
D. Both, RNA and DNA transposons, are found in eukaryotes.
Choose correct combination.
a. A and C
b. B and C
c. A and D
d. B and D

4. Which one of the following statements about LEAFY (LFY) a regulatory gene in Arabidopsis thaliana, is correct?
a. LEAFY (LFY) is involved in floral meristem identity.
b. LEAFY (LFY) is involved in leaf expansion.
c. LEAFY (LFY) is involved in root meristem identity.
d. LEAFY (LFY) is responsible for far-red light mediated seedling growth.

5. Nitrogen gas is reduced to ammonia by nitrogen fixation method. In order to execute the process, which one of the following compounds is usually required?
a. ATP
b. GTP
c. UDP
d. ADP

6. The quantum yield of oxygen evolution during photosynthesis drastically drops in far-red light. This effect is known as:
a. Far red drop.
b. Red drop.
c. Blue drop.
d. Visible spectrum drop.


7. In an alpha helical polypeptide, the backbone hydrogen bonds are between
a. NH of n and CO of n+4 amino acids.
b. CO of n and NH of n+3 amino acids.
c. CO of n and NH of n+4 amino acids.
d. NH of n and CO of n+3 amino acids.


8. The S wave of normal human ECG originates due to

a. Septal and left ventricular depolarization.
b. Late depolarization of the ventricular walls moving back toward the AV junction.
c. Left to right septal depolarization.
d. Repolarization of atrium.

9. Cystic fibrosis transmembrane conductance regulator (CFTR) is known to control the transport of which ion?
a. Ca⁺²
b. Mg⁺²
c. HCO₃^-
d. Cl^-

10. In type II splicing
a. a ‘G-OH’ from outside makes a nucleophilic attack on 5’P of first base of intron
b. a free 2’O of an internal adenosine makes a nucleophilic attack on 5’P of first phase of intron
c. a 3’O of an internal adenosine makes a nucleophilic attack on 5’P of first base of intron
d. the hydrolysis of last base of exon is carried out by U2/U4/U6

Answers with Explanation

1. c. Long chain saturated fatty acids
Explanation: Long chain saturated fatty acids will decrease the fluidity of the plasma membrane. Bacteria synthesise such fatty acid to survive under high temperature  (Refer: Plasma membrane and membrane fluidity)

2. a. Sucrose
Explanation: Sucrose is translocated through phloem in plants.

3. d. B and D
Explanation: Most transposons in bacteria are DNA and eukaryotes have both DNA and RNA

4. a  LEAFY (LFY) is involved in floral meristem identity.
Explanation: LEAFY is a floral meristem identity gene. (Refer: ABC model of Flower Development)

5. a. ATP
Explanation: The process is coupled to the hydrolysis of 16 equivalents of ATP and is accompanied by the co-formation of one molecule of H₂.

6. b. Red drop.
Explanation: The sudden fall in the photosynthetic yield in far-red region of the solar radiation spectrum is called Emerson’s “red drop”.

7. c. CO of n and NH of n+4 amino acids.

Explanation: The alpha helix is a common secondary structure of proteins. To fotm the helix, the bond is between C=O group of the first amino acid with NH group of the fifth amino acid ( n+4 hydrogen bonding). (Refer: Bonds in Protein structure)


8 b. Late depolarization of the ventricular walls moving back toward the AV junction.
Explanation: The S wave is the first negative deflection after the R wave. It represents the late ventricular depolarisation.

9. d. Cl^-
Explanation: Cystic fibrosis transmembrane conductance regulator (CFTR) is a membrane protein and chloride channel in vertebrates that is encoded by CFTR gene. (Refer: Autosomal Recessive  Disorders - Cystic fibrosis)
10. b. a free 2’O of an internal adenosine makes a nucleophilic attack on 5’P of first phase of intron