CSIR JRF NET Life Sciences December 2008 Previous Year Question Paper with Answer Key and Explanations Part 2

CSIR NET Life Sciences: December 2008: Part 2

(1). Pick out the correct taxonomic hierarchy in zoological systematics.

a.       Phylum – Class – Order – Family – Genus
b.      Class – Phylum – Order – Family – Genus
c.       Phylum – Class – Family – Order – Genus
d.      Phylum – Class – Order – Genus – Species

(2). In molecular systematics of animals, which for the following candidate gene have been extensively used?

a.       DNA Polymerase
b.      Cytochrome C
c.       RNA Polymerase
d.      Collagen

(3). What would be the effect of increasing humidity in the rate of transpiration?

a.       Rate of transpiration will decrease
b.      Rate of transpiration will increase
c.       Initially the rate will be low then it will be high
d.      Rate of transpiration will be unaffected

(4). The most probable place where life would have originated _________.

a.       Outer space
b.      Barren rocks
c.       In oceans
d.      Deep hydrothermal vents

(5).  As we move from one geographical region to next neighbouring region, species diversity tends to change. It is termed as

a.       α-diversity
b.      β-diversity
c.       γ-diversity
d.      δ-diversity

(6).  Which of the following factor is least responsible for genetic drift?

a.       Migration
b.      Founder effect
c.       Bottle neck phenomenon
d.      Restriction of resources

(7). In stomach, the mucus which protect the epithelial lining of stomach, is secreted by:

a.       Goblet cells
b.      Parietal cells
c.       Microvilli
d.      Aciner cells

(8). In a population with Hardy-Weinberg equilibrium, two alleles ‘b’ and ‘B’ showed an allelic frequency of 0.7 and 0.3 respectively. How many individuals in a sample of 250 from this population can be expected to be heterozygous (bB)?

a.       55
b.      105
c.       110
d.      42

(9). Chitin is a major cell wall component of __________

a.       Bacteria
b.      Arthropods
c.       Fungus
d.      Mollusks

(10).  The anti-cancerous drug obtained from Catharanthus roseus is__________.

a.       Taxol
b.      Vincristine
c.       Colchicine
d.      Serpentine

(11).  Yeast with petite colony when crossed with wild type generates no petite colony. The most probable mode of inheritance is __________

a.       Chloroplast
b.      Mitochondria
c.       Episomal
d.      Nuclear

(12).  An oligonucleotide DNA sequence tagged with fluorescent tag used to identify unknown gene by hybridization is termed as

a.       Probe
b.      Reporter gene
c.       Ligand
d.      c-DNA

(13).  Bacteria undergo multiplication by:

a.       Binary fission
b.      Mitosis
c.       Fission and Mitosis
d.      Fragmentation

(14).  Bacterial DNA polymerase I lack which of the following activity?

a.       5’ → 3’ polymerase activity
b.      3’ → 5’ polymerase activity
c.       5’ → 3’ exo-nuclease activity
d.      3’ → 5’ exo-nuclease activity

(15).  A cross between a red eyed male fly and a white eyed female fly produces red eyed female and white eyed male progenies. While reciprocal cross produces all offspring with red eyes. The trait for eye colour is:

a.       Sex linked traits
b.      Sex influenced trait
c.       Sex linked homogametic male
d.      Sex linked heterogametic male

(16).  The natural habitat of Nilgiri-tahr is

a.       Shola grasslands
b.      Nilgiri forests
c.       Shola grasslands and Nilgiri forests
d.      At high altitudes of South-Western Ghats

(17).  When releasing factor binds to stop codon on m-RNA during translation, the synthesized peptide chain is transferred to

a.       t-RNA
b.      Water
c.       H+
d.      Amino acids

(18).  Location of Glutamate synthetase enzyme in plants is:

a.       Only cytoplasm
b.      Only chloroplast
c.       Both in cytoplasm and chloroplast
d.      In mitochondria

(19).  Which is true for β-oxidation of fatty acids

a.       Formation of malonyl CoA
b.      Formation of acetoacyl ACP
c.       Transport of Acyl CoA into mitochondria
d.      Use of NADPH2

(20).  The radio isotope which is usually incorporated into thymine to study DNA replication process is

a.       32P
b.      35S
c.       3H
d.      14C

(21).  Enzymes accelerates rate of reaction by:

a.       Lowering number of transition states
b.      Lowering the activation energy of highest transition state
c.       Providing energy to substrate
d.      Providing more chance to substrates to react together

(22).  Enzyme never interfere with:

a.       Free energy of reaction
b.      Rate of reaction
c.       Activation energy of transition state
d.      Reaction equilibrium

(23). Globular proteins when treated with organic solvents get denatured. The main interaction which is affected on treatment with organic solvent is:

a.       Hydrogen bonds
b.      Covalent bonds
c.       Ionic interactions
d.      Hydrophobic interactions

(24).  Which region of visible light is most useful for photosynthesis?

a.       Blue and red
b.      Green and red
c.       Violet and blue
d.      Green and blue

(25).  Fog, which is commonly observed during winter is mainly seen at

a.       Low altitude with pollution
b.      High altitude without pollution
c.       High altitude with pollution
d.      Low altitude without pollution

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Answer key with explanations (MCQ 015):

1. Ans. (a). Phylum – Class – Order – Family – Genus

This arrangement is called ‘Taxonomic Hierarchy”. In the taxonomy of animals there are eight positions (ranks) (1) Domain, (2) Kingdom, (3) Phylum, (4) Class, (5) Order, (6)Family, (7) Genus and (8) Species. In plant systematics, majority of taxonomists follows six hierarchical ‘ranks’ and they are (1) Division, (2) Class, (3) Order, (4) Family, (5) Genus and (6) Species.

2. Ans. (b). Cytochrome C

Cyt-c is a hemeprotein found in the inner mitochondrial membrane, is one of the components of mitochondrial electron transport system (ETS).

rbcl (RuBisCo large subunit), maturase K (matK), 16S rRNA, 18S rRNA are other candidate genes used in molecular systematics.

rbcl is best for plants

matK is best candidate for angiosperm barcoding

Cyt-c is commonly used for molecular systematics of animals

16S rRNA is used for the molecular systematics of prokaryotes (bacteria, cyanobacteria)

3. Ans. (a). Rate of transpiration will decrease

During humid weather, the surroundings of the leaves will be crowded by water vapour molecules and it will reduce the diffusion of water from leaves to the atmosphere and hence transpiration will be reduced

4. Ans. (d). Deep hydrothermal vents

5. Ans. (d). β-diversity

Biodiversity represent the richness of species in a geographical area. α-diversity, β-diversity and γ-diversity are the various levels of measuring the biodiversity.

α-diversity: measure the number of species in a single community (simply it is species richness). It is used to compare the number of species in different communities.

β-diversity: it is the degree to which species composition changes along with an environmental gradient. Example: beta diversity is high, if the species composition of moss community changes successively at higher elevations on a mountain slope, and similarly beta diversity is low if the same species of moss occupy the whole mountain side

γ-diversity: measures the biodiversity of large geographic area. It is a rate at which additional species are encountered as geographical replacements within a habitat type in different localities. Gamma diversity is a species turnover rate with distance between sites of similar habitat or with expanding geographic areas.

6. Ans. (d). Restriction of resources

Migration, Founder effect and Bottle neck phenomenon causes rapid changes in genetic constitution of a population and thereby it affect the Hardy-Weinberg equilibrium in the population.

Genetic drift: change in the allelic frequency in a population due to evolutionary forces such as migration, mutation, selection, bottle neck phenomenon, founder effect etc.

Hardy-Weinberg equilibrium: The relative frequencies of various kinds of genes and alleles in a large and randomly mating (panmictic) population tend to remain constant from generation to generation in the absence of mutation, selection and gene flow

A population in Hardy-Weinberg equilibrium DONOT undergoes EVOLUTION (i.e., for the evolution to proceed, a population should break the Hardy-Weinberg equilibrium.)

Bottle neck phenomenon (= population bottleneck): sharp decline in the population size due to any environmental or anthropological causes which results in the reduction of gene pool.

Founder effect: loss of genetic variability in a newly established population by a very small number of individuals from a larger population. Population bottleneck may cause founder effect in a population.

7. Ans. (a). Goblet cells

Goblet cells: modified columnar epithelial cells with the function to secret mucus

Parietal cells (oxyntic cells): modified epithelial gastric cells which secrete hydrochloric acid (HCl) and intrinsic factors in the stomach. They contain a network system called canaliculi, which secrete the HCl molecule by active transport. The H+/K+ ATPase in the parietal cell transport H+ ions against concentration gradient

Intrinsic factor (IF): glycoproteins secreted by parietal cells which are required for the absorption of vitamin B12 in the small intestine

Microvilli: microscopic cellular membrane protrusions that increase the surface area of cells without any increase in the total volume of cells and their main function are adsorption, secretion and adhesion.

Chief cells (peptic cells, or zymogenic cells): secrete digestive enzymes in the stomach as zymogens (inactive enzymes). Major zymogen of chief cells are pepsinogen and gastric lipase

8. Ans. (b). 105

9. Ans. (c). Fungus

Cell wall of fungi: chitin
Cell wall of blue green algae: peptidoglycan
Cell wall of algae and plants: cellulose
Cell wall of bacteria: peptidoglycan (mucopeptide)
Cell wall of ascidians: tunicine (animal cellulose). The test of ascidians contain animal cellulose traditionally called as tunicine.

10.  Ans. (b). Vincristine

Vinca rosea is the old name of Catharanthus roseus. Vincristine and Vinblastine are the two vinca alkaloid obtained from Catharanthus roseus, extensively used as chemotherapeutic agent in the treatment of cancer.

Taxol and colchicine are other anti-cancer drug of plant origin

anticancerous drugs from plants

Serpentine is an alkaloid obtained from Rauvolfia serpentine (Apocynaceae) to treat against higher blood pressure

11.  Ans. (b). Mitochondria

Mitochondrial inheritance causes maternal influence (cytoplasmic inheritance).

Episomes: a category of plasmid which are able to integrate in the host genome

12.  Ans. (a). Probe

Reporter gene: genes which are attached to the regulatory sequence of gene of interest. They act as selectable marker in the experiment setup and enable the researcher to monitor the expression of targeted gene of interest. Example for reporter genes: lacZ (β-galactosidase), cat (chloramphenicol acetyltransferase), GFP (green fluorescent protein), RFP (red fluorescent protein) etc.

13.  Ans. (a). Binary fission

Mitosis and meiosis are completely absent in bacteria

14.  Ans. (b). 3’ → 5’ polymerase activity

DNA polymerase I (Pol I) is the first DNA polymerase enzyme discovered (by Arthur Kornberg in 1956 from E. coli, known as ‘konberg’ enzyme). Pol I is present in all prokaryotes. The gene that code DNA polymerase I in bacteria is called polA. DNA polymerase enzyme is an example for enzyme having processivity so that it can catalyze consecutive reactions without releasing its substrate.

The Pol I enzyme processes four enzymatic activities:

5’→3′ DNA dependent DNA polymerase activity for DNA replication
3’→5′ exonuclease activity for proofreading
5’→3′ exonuclease activity for nick translation during DNA repair
5’→3′ RNA dependent DNA polymerase activity (with less efficiency)

Klenow fragment: Pol I is extensively used in molecular biology researches. The 5’→3’exonuclease activity of this enzyme make it unsuitable for research applications. Klenow fragment is the functional enzyme portion left after the Pol I holoenzyme was treated with protease subtilisin. The subtilisin treatment remove the 5’→3’exonuclease activity of Pol I holoenzyme without altering the other functions so that it can be used in research applications.

Exo-Klenow fragment: It is a DNA Pol I Klenow fragment from which the  3′ → 5’ exonuclease activity is removed by inducing site specific mutation in the genes which code the the Klenow fragment. Exo-Kleno fragment will only have the 5′ → 3′ polymerase activity. Exo-Klenow fragment is used in fluorescent labeling reactions for micro array experiments

15.  Ans. (d). Sex linked heterogametic male

Here the sex determination is heterogametic with heterogametic male and homogametic female. For example in the case of human, individuals with XX sex chromosome constitution will be female and that of XY will be males. Unlike the classical Mendelian inheritance, where the reciprocal cross will also give same results, here in heterogametic sex-linked genes the results will be different with change in the sex of the parent (i.e., reciprocal crosses will give different results)

Reciprocal cross: in reciprocal cross the sex of the parents will be altered in the second hybridization without altering the genotype of the parent. Example: if in first cross the female parent used is red eyed and the male parent used is wild type, in the next cross the female parent will be wild type and the male parent will be red eyed.

16.  Ans. (d). At high altitudes of South-Western Ghats

17.  Ans. (b). Water

18.  Ans. (c). Both in cytoplasm and chloroplast

Glutamine synthetase is an important enzyme involved in nitrogen metabolism. It catalyze the production of glutamine by the condensation of glutamate and ammonia with the presence of ATP.

19.  Ans. (c). Transport of Acyl CoA into mitochondria

Formation of malonyl CoA, formation of acetoacyl ACP and use of NADPH2 are true for fatty acid synthesis.

The site of beta-oxidation of fatty acid is mitochondria.

20.  Ans. (c) 3H

32P is used for the labeling of DNA (because DNA contains phosphorus), it is a beta ray emitter with half-life period of 14.29 days.

35S is used for labeling protein (since proteins contain two sulfur containing amino acids, namely cysteine and methionine). The half-life period is 87 days.

3H is the isotope of hydrogen called tritium. It is a beta emitter with a half-life of ~ 12.23 years.

3H incorporated thymidine is used to quantify the DNA in ‘thymidine incorporation assay’. The thymidine incorporation assay utilizes a strategy wherein a radioactive nucleoside, 3H-thymidine, is incorporated into new strands of chromosomal DNA during mitotic cell division. A scintillation beta-counter is used to measure the radioactivity in DNA recovered from the cells in order to determine the extent of cell division that has occurred in response to a test agent.

14C is the radioactive isotope of carbon, mainly used in physiological experiments to trace the path of biomolecules. It also used in radio-carbon-dating of fossils. It is a beta emitter with a half-life period of 5,730±40 years.

21.  Ans. (b). Lowering the activation energy of highest transition state

22.  Ans. (d). Reaction equilibrium

23.  Ans. (d). Hydrophobic interactions

24.  Ans. (a). Blue and red

25.  Ans. (d). Low altitude without pollution

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