NET XL December 2015 Question Paper with Answer Key (Part II)

Life Sciences NET Dec 2015

Previous Year Question Papers of CSIR – UGC /JRF/NET: Life Science Examination, December 2015 (II)
(Original Question Paper with Answer Key, Explanations and References)

PART: B (Questions 41 – 60)

(41). Phenylalanine, a precursor of most of the phenolics in higher plants is a product of which one of the following pathways?

a.       Shikimic acid pathway
b.      Malonic acid pathway
c.       Mevalonic acid pathway
d.      Methylerythritol pathway

Ans. (a)

Shikimic acid pathway is a metabolic seven step pathway in bacterial, fungi, and plants for the synthesis of aromatic amino acids such as Phenylalanine, tyrosine and tryptophan. Shikimic acid pathway is completely absent in animals and hence all the above amino acids are essential amino acids to animals

Mevalonic acid pathway is for the production of  isoprenoids.

(42). For which one of the following physiological studies 12CO2 and 13CO2 are used?

a.       Estimate the rate of photosynthesis
b.      Determine rate of photorespiration
c.       The ratio of C4 and CAM pathways of CO2 fixation
d.      The ratio of C3 and C4 pathways of CO2 fixation

Ans. (d)

(43). Gibberellic acid (GA) controls seed germination by directing breakdown of the stored starch. In which one of the following tissues of the barley seed, – amylase gene is induced in response to GA?

a.       Endosperm
b.      Coleoptile
c.       Aleurone layer
d.      Embryo

Ans. (c)

During seed germination, plant embryo produces gibberellin which triggers the aleurone cells to release α-amylase for the hydrolysis of starch stored in the endosperm.

(44). The photosynthetic assimilation of atmospheric CO2 by leaves yield sucrose and starch as end products of two gluconeogenic pathways that are physically separated. Which one of the following combination of cell organelles are involved in such physical separation of the process?

a.       Sucrose in cytosol and starch in mitochondria.
b.      Sucrose in chloroplasts and starch in cytosol.
c.       Sucrose in mitochondria and starch in cytosol.
d.      Sucrose in cytosol and starch in chloroplasts.

Ans. (d)

(45). A diabetic patient developed metabolic acidosis resulting in deep and rapid breathing which is called-

a.       Kussmaul breathing
b.      Cheyne-Stokes respiratory pattern
c.       Apneustic breathing
d.      Periodic breathing

Ans. (a)

(46). Which one of the following is NOT involved with the pacemaker potential of heart?

a.       “h”- channel
b.      Transient calcium channel
c.       Long-lasting calcium channel
d.      “f”- channel

Ans. (c)

(47). You are asked to identify the stage of estrus cycle in vaginal smear of a mouse containing large number of leukocytes and very few nucleated epithelial cells. Which one of the following will be the correct stage of estrous cycle?

a.       Early estrus, late proestrus
b.      Late estrus, early metestrus
c.       Late metestrus, early diestrus
d.      Late diestrus, early proestrus

Ans. (d)

(48).  Which one of the following neurotransmitters is secreted by the pre-ganglionic neurons of sympathetic nervous system?

a.       Epinephrine
b.      Acetylcholine
c.       Dopamine
d.      Norepinephrine

Ans. (b)

(49).  Following is a hypothetical biochemical pathway responsible for pigmentation of leaves. The pathway is controlled by two independently assorting genes ‘A’ and ‘B’ encoding enzymes as shown below. Mutant alleles ‘a’ and ‘b’ code for non- functional proteins.

UGC CSIR JRF NET Life Sciences

What is the expected progeny after selfing a plant with the genotype AaBb ?

a.       Green (9): White (4): Yellow (3)
b.      Green (9): Yellow (4): White (3)
c.       Green (9): Yellow (6): White (1)
d.      Green (9): White (7)

Ans. (a)

(50).  Mutation in gene ‘X’ leads to lethality in a haploid organism. Which one of the following is best suited to analyze the function of gene ‘X’?

a.       Pleiotropic mutants
b.      Temperature-sensitive mutants
c.       Recessive mutants
d.      Mutants with low penetrance

Ans. (b)

(51).  The following pedigree chart shows inheritance of a given trait

life science net jrf dec 2015

The trait can be called

a.       autosomal dominant
b.      autosomal recessive
c.       X-linked dominant
d.      sex limited

Ans. (a)

(52).  In a heterozygous individual for a given gene, if a crossing over has occurred between the gene locus and the centromere of the chromosome, the segregation of the two alleles of the given gene will occur during meiosis at:

a.       either anaphase I or anaphase II
b.      anaphase I only
c.       anaphase II only
d.      both anaphase I and II

Ans. (c)

(53).  Most members of bryophyte phylum Anthocerophyta are characterized by

a.       gametophyte with single chloroplast per cell and multicellular rhizoids; sporophyte without stomata.
b.      gametophyte with single chloroplast per cell and unicellular rhizoids; sporophyte with stomata.
c.       gametophyte with multiple chloroplasts per cell and unicellular rhizoids; sporophyte without stomata.
d.      gametophyte with single chloroplast per cell and multicellular rhizoids; sporophyte with stomata.

Ans. (b)

(54).  Identify the correct match between the animal (flatworm, earthworm, roundworm) and its body cavity type (acoelomate, coelomate, pseudo- coelomate):

a.       Roundworm – pseudocoelomate; Earthworm – acoelomate; Flatworm – coelomate
b.      Roundworm – acoelomate; Earthworm – coelomate; Flatworm – acoelomate
c.       Roundworm – pseudocoelomate; Earthworm – coelomate; Flatworm – acoelomate
d.      Roundworm –coelomate; Earthworm – pseudocoelomate; Flatworm – acoelomate

Ans. (c)

(55).  Which one of the following gymnosperm phyla produces motile sperms, bears ovulate and microsporangiate cones on separate plants and has fleshy, coated seeds?

a.       Coniferophyta
b.      Cycadophyta
c.       Ginkgophyta
d.      Gnetophyta

Ans. (c)

(56).  According to 2014 IUCN Red List, which of the following vertebrate classes has the largest percentage of threatened species?

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

Ans. (d)

(57).  In the following equations

(a). dN/dt = rN
(b). NT = Noert
(c). dN/dt = rN ((K-N)/K)
(d). dN/dt = rN X N/K

Exponential population growth is described by

a.       a and b.
b.      a only.
c.       c only.
d.      b and d.

Ans. (a)

(58).  Which gas does NOT contribute to global warming through its greenhouse effect?

a.       Nitrous oxide
b.      Methane
c.       Carbon dioxide
d.      Nitric oxide

Ans. (d)

(59).  A red coloured tubular flower without any odour is most likely to be pollinated by

a.       beetles.
b.      bees.
c.       butterflies.
d.      birds.

Ans. (d)

(60).  Which one of the following conditions is NOT likely to favour male monogamy?

a.       When the male has to guard his mate against mating by another male.
b.      When the male wants to spend more time for foraging.
c.       When the male has to assist the mate in brood and nestling care.
d.      When the female guards her mate against seeking other females to mate.

Ans. (b)

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