CSIR JRF NET Life Science December 2008 Previous Year Questions with Answer Key and Explanations

CSIR NET Life Science December 2008 Part 1

*(1). Which of the following soil will be most porous:
a.       Sandy loam
b.      Clay loam
c.       Clay

(2). Photosynthetic formation of glucose can be sited as an example for:
a.       Oxidation
b.      Reduction
c.       Condensation
d.      Fixation

(3). Members of which family has been extensively employed as phyo-remediation agents for the removal of contaminates from soil
a.       Poaceae
b.      Brassicaceae
c.       Malvaceae
d.      Annonaceae

(4).  Which of the following cancer can be prevented by vaccination?
a.       Oral cancer
b.      Cervical cancer
c.       Breast cancer
d.      Colon cancer

(5). Which of the following is NOT involved in plant defense signaling pathway in plants?
a.       Gibberellic acid
b.      Ethylene
c.       Salisylic acid
d.      Jasmonic acid

(6). During the germination of barley seeds, enzymes for mobilization of reserve food materials for developing embryo are secreted by:

a.       Endosperm
b.      Embryo
c.       Aleurone layer
d.      Embryonic leaves

(7). During brain mapping, the electrical activity of brain can be recorded by the method ____.

a.       FMRI
b.      ECG
c.       EEG
d.      Polygraphy

(8). The best system which can be adopted for gene therapy is__________.

a.       P elements
b.      Cre-Lox system
c.       Non-homogenous recombination
d.      Ac-Ds elements

(9). Which of the following is NOT a cell adhesion protein?

a.       Cadherin
b.      Integrin
c.       Selectin
d.      Clathrin

(10).  Pick out the miss matched pair from the following:

a.       Choanocytes – Profera
b.      Malphigian tubules – Arthropods
c.       Clitellum – Annelids
d.      Cnidocytes – Mollusc

(11).  The main force in membrane resealing of ruptured biomembrane in aqueous environment is:

a.       Hydrophobic forces between membrane lipids
b.      Covalent forces between membrane lipids
c.       Forces between protein and lipids
d.      Ionic interactions between membrane lipids

(12).  What would happen if lysosome membrane leaks its digestive enzyme in cytosol:

a.       Acid hydrolases will be inactivated
b.      Acid hydrolases will digest the cellular components
c.       pH of cell will increase
d.      it will cause I-cell disease

(13).  Regulation of trp operon by binding of tryptophan to trp repressor is termed as:

a.       Repression
b.      Induction
c.       Anti-termination
d.      Attenuation

(14).  In salt tolerance plants, the excess salt is transported to vacuole by:

a.       Na –H+ antiporter
b.      Na – K+ pump
c.       Na – Cl symporter
d.      Na – H+ ATPase

(15).  Individuals having X chromosome and shot arm of Y chromosome are Males, while individuals having X chromosome and long arm of Y chromosome are female. This shows that_____

a.       Genes for maleness are located on short arm of Y chromosome
b.      Genes for maleness are located on long arm of Y chromosome
c.       Genes for maleness are located on the X chromosome
d.      Male determining genes are located on Y chromosome

(16).  Xeroderma pigmentosum is a genetic disorder caused by error in_______.

a.       Base excision repair mechanism
b.      Nucleotide excision repair mechanism
c.       Direct repair mechanism
d.      DNA replication mechanism

(17).  Which of the following antibiotic inhibit 80S ribosomes

a.       Tetracycline
b.      Strptomycin
c.       Cyclohexamide
d.      Chloramphenicol

(18).  The toxic mechanism of diphtheria toxin is by ___________.

a.       ADP ribosylation of EF-2
b.      ADP ribosylation of EF1α
c.       Blocking the activity of RNA polymerase
d.      Blocking DNA replication process

(19).  A major functional difference between the succinyl CoA-synthetase of plant and animal cell mitochondria is that:

a.       Does not produce ATP in plant cells
b.      Produce UTP in plant cells
c.       Produce ATP in plants and GTP in animals
d.      Produce GTP in plants and ATP in animals

(20).  Which of the following is NOT commonly considered as a potential pollutant

a.       CO
b.      CO2
c.       SO2
d.      NOx

(21).  Lateral roots in plants are originated from

a.       Pericycle
b.      Cortex
c.       Pith
d.      Endodermis

(22).  Choose the plant family with characteristic umbel inflorescence:

a.       Asteraceae
b.      Acanthaceae
c.       Apiaceae
d.      Poaceae

(23).  The distance between two gens ‘A’ and ‘B’ is 10 cM. What is the chance of getting a progeny with genotype Aabb, if  AaBb is test crossed?

a.       5%
b.      10%
c.       11%
d.      90%

(24).  Circadian rhythms in plants are chiefly regulated by______.

a.       Phycobillins
b.      Phytochromes
c.       Phototropins

(25).  As per the IUCN red data list, which taxa contains maximum number of endangered and critically endangered species?

a.       Amphibians
b.      Reptiles
c.       Mammals
d.      Birds


Answers with explanations (MCQ 0014)

1. Ans. (a). Sandy loam

Porosity of the soil increases with the increase in the particle size of soil. Sand particles will have larger size than clay particles in the soil.

2. Ans. (b). Reduction

Reduction is a synthetic process (fusion of simple molecules to form large complex molecules)
Oxidation and reduction can be explained based on three criteria:
I. Oxygen: Oxidation is addition of oxygen while reduction is removal of oxygen
II. Electrons: Oxidation is Loss of Electrons (OIL), reduction is gain of electrons
II. Protons: Oxidation is removal of protons, reduction is addiction of protons

Condensation: a type of reaction where a covalent bond is formed with the removal of one molecule of water (elimination of water = elimination reaction) between two reactive functional groups. Example: Peptide bond formation in proteins, ester bond formation in lipids, glycosidic linkages in carbohydrates etc.

3. Ans. (b). Brassicaceae

Old name of Brassicaceae is Cruciferae

Phytoremediation: use of plants for the in-situ removal of toxic components from soil, air or water.

4. Ans. (b). Cervical cancer

Cervical cancer is caused by Human Papillomavirus (HPV). Vaccination against HPV can prevent the occurrence of cervical cancer in human. Similarly by vaccination against Human Hepatitis B virus (HBV), hepatocellular carcinoma (HCC) can be prevented to some extent. In the case of HCC, HBV infection is not the only reason, so vaccination cannot provide a complete protection against HCC.

5. Ans. (a). Gibberellic acid

6. Ans. (c). Aleurone layer

7. Ans. (c). EEG

EEG (Electroencephalography)

FMRI: (Functional Magnetic Resonance Imaging): An MRI technology to monitor brain activity by detecting associated changes in blood flow.

ECG (Electrocardiography): to measure the electrical activity of heart over a period of time.

Polygraphy: a lie detection method in criminology by measure several parameters such as blood pressure, pulse, respiration rate etc. when the person is answered for a series of question associated with the crime.

8. Ans. (b). Cre-Lox system

Cre-Lox system: A site specific recombination system which can be used to produce conditional knockouts by inducing mutation in targeted genes either by deletion, inversion or translocation. This system utilizes the Cre recombinase enzyme and LoxP site of Bacteriophage P1 to induce knockouts.

P – Element: a transposon in Drosophila melanogaster and it is widely used to induce mutation in fruit flies for genetic research.

Non-homologous recombination: a non-allelic recombination that occurs between two non-allelic locations due to sequence similarities in the DNA.

Ac-Ds elements: are transposons of maize first discovered by Barbara McClintoc. Ac stands for Activator and Ds stands of Dissociation.

9. Ans. (d). Clathrin

Clathrin is protein and whose major function is in the formation of coated vesicles. Three clathrin molecules associates to forms a triskelion shaped structure which later assembled to form the vesicles.

Cadherin: calcium dependent trans-membrane adherence protein of cells.

Integrin: Membrane protein receptors that bridges cell wall and extra cellular matrix (ECM).

Selectin: A specific sugar binding protein (hence lectin) of adhering molecules the extracellular matrix

10.  Ans. (d). Cnidocytes – Mollusc

Cnidocyte (also called as cnidoblast or nematocyte) is a giant explosive secretary cell of phylum Cnidaria (corals, sea anemones, hydrae, jelly fish etc.). The members of Cnidaria use cnidocytes for prey capturing and also for defense from predators.

Choanocytes:  (also called collar cells) are cells that line the interior of asconoid, syconoid and leuconoid body type sponges that contain a central flagellum or undulipida, surrounded by a collar of microvilli which are connected by a thin membrane. This constitutes the Choanoderm, a type of cell layer found in sponges. Malphigian tubules: excretory and osmo-regulatory system found in insects (Arthropods).

Clitellum: It is a glandular, non-segmented section of the body near the head region of earthworms and leeches that secretes a viscid sac. The main function of clitellum is to store egg cells.

11.  Ans. (a). Hydrophobic forces between membrane lipids

Hydrophobic interactions between the tails of membrane lipids and hydrophilic interaction of head portion of membrane lipid and water assist the packing of lipids in bio-membranes

12.  Ans. (a). Acid hydrolases will be inactivated

Acid hydrolases are enzyme, present in lysosome, whose optimum pH is acidic condition. When it is released into the cytoplasm which is having neutral to slightly alkaline pH (ph of human cytoplasm is 70.0 to 7.4), the enzyme will be inactivated.

13.  Ans. (a). Repression

trp-operon is the first repressible operon discovered (by Jacques Monod in 1952).

trp-operaon is a repressible operon: the operon will be switched off with the tryptophan.

Attenuation: it is the additional (second) mechanism of negative feedback in try-operon. Attenuation responds with the concentration of charged t-RNAtrp in the cell. Attenuation can repress the trp operon by a factor of 10 fold (The repressor can repress by a factor 70). Thus altogether a total of 700 fold repression is achieved with repression and attenuation.

Anti-termination:  is a mechanism in prokaryotes to overcome premature termination of transcription by RNA polymerase enzyme. By this mechanism, the cell can either switch on or off one for few genes located at the end of an operon by ignoring the termination signal in the DNA. Anti-termination is also present in some phages to regulation the progression of one stage to next during its life cycle.

14.  Ans. (a). Na – K+ antiporter

15.  Ans. (a). Genes for maleness are located on short arm of Y chromosome

16.  Ans. (b). Nucleotide excision repair mechanism

17.  Ans. (c). Cyclohexamide

Tetracycline: Protein synthesis inhibitor, inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation complex.

Streptomycin: Protein synthesis inhibitor, bins to the 16S rRNA of 30S subunit of ribosome and thus interfere with the binding of formyl-methionyl-tRNA and hence initiation of protein synthesis is inhibited.

Chloramphenicol: Inhibit the peptidoglycan cell wall synthesis in bacteria by inhibiting the enzyme transpeptidase. Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell wall.

Cyclohexamide: An antibiotic which inhibit protein synthesis in eukaryotes by interfering the translocation process and thus inhibit the translational elongation process. It is produced by the bacterium Streptomyces griseus

18.  Ans. (a). AND ribosylation of EF-2

Diphtheria toxin is a protenacious exotoxin produced by Corynebacterium diphtheria, which causes diphtheria in human. Diphtheria toxin inhibits protein synthesis by inhibiting the eukaryotic Elongation Factor 2 (eEF2) by the transfer of NAD+ to the diphthamide residue in the elongation factor (eEF2) by ADP ribosylation.

Diphthamide: it is a modified histidine residue found in the eukaryotic Elongation Factor 2 (eEF-2)

19.  Ans. (c). Produce ATP in plants and GTP in animals

20.  Ans. (b). CO2

21.  Ans. (a). Pericycle

22.  Ans. (c). Apiaceae

23.  Ans. (a). 5%

24.  Ans. (c). Phototropins

Phototropins are protenacaceous (flavor-proteins) photoreceptors that mediate phototropism in higher plants.

Phycobilins are the light absorbing pigments present in cyanobacteria and in the chloroplasts of red algae.

Phytochromes are photoreceptor pigments in plants to detect light

25.  Ans. (a). Amphibians

As of 2015, 792 amphibians, 358 reptiles, 482 mammals and 419 bird species are endangered

As of 2015, 522 amphibians, 174 reptiles, 212 mammals and 213 bird species are critically endangered

About 30 % of all amphibians are under the threat categories of ‘vulnerable’ ‘endangered’ and ‘critically endangered’

*Questions prepared from 2008 CSIR question paper

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