CSIR JRF NET Life Sciences June 2016
CSIR NET Model Questions Part 5 (CSIR MCQ – 05)
Biology MCQ (Multiple Choice Questions in Life Science)
(Sample/Model/Practice Questions for JRF/NET Life Science Examination, ICMR JRF, DBT JRF, GATE, ICAR NET, PG Entrance)
1. If offspring of heterozygous parents (Aa at a single locus) are 25 percent AA, 50 percent Aa and 25 percent aa, then all of the following are true except:
a. The parents are diploid organisms
b. The allele is recessive lethal
c. The alleles assort independently
d. The gametes combine at random
2. A honey bee colony consists of:
a. Equal number of males and females with all able to reproduce
b. Mostly males, with only a single male being able to reproduce
c. Mostly females, with only a single female being able to reproduce
d. Equal number of males and females, with none able to reproduce sexually
3. Carbon sequestration refers to:
a. The sale of carbon credits in the international market
b. The process of capture and long-term storage of atmospheric oxygen
c. The release of carbon, as CO2, into the atmosphere
d. The accumulation of carbon in the atmosphere
4. The reason for the melting of DNA double helix at specific temperature is:
a. Loss of base stacking energy
b. The double helix is intrinsically unstable
c. The single helix is more stable as compared to the double helix
d. DNA double helix is a co-operative structure stabilized by hydrogen bonds and base pairing
5. The interaction of enhancer and promoter elements in eukaryotes is facilitated by:
a. Zinc finger
b. DNA looping
c. Helix turn helix
d. Palindromic sequence
6. Which of the following RNA is involved in gene expression regulation?
a. rRNA
b. 5.5S rRNA
c. tRNA
d. miRNA
7. Temperature dependent sex determination mechanism is observed in
a. Drosophila
b. Amphibians
c. Reptiles
d. Sea urchins
8. If the ratio of (A + G)/(T + C) in one strand of DNA is 0.70, what is the same ratio in the complementary strand?
a. 0.70
b. 1.43
c. 0.35
d. 0.30
9. In the resting state of a neuron, the axonal membrane is
a. Comparatively more permeable to K+ ions and nearly impermeable to Na+ ions
b. Comparatively more permeable to Na+ ins and nearly impermeable to K+ ions
c. Equally permeable to both Na+ and K+ ions
d. Impermeable to both Na+ and K+ ions
10. Why do glycolipids exist almost exclusively on the exterior side, but not on the cytoplasmic side of the cell membrane?
a. The inner layer of the membrane is not thick enough to accommodate carbohydrates
b. Carbohydrates are added only to lipids on the luminal side of the ER and Golgi
c. Flippases more the glycolipids to the exterior side of the membrane
d. Carbohydrates are enzymatically removed from the cytoplasmic side of the membrane
11. Co-transformation between two genes is more likely if they are:
a. Close to one another
b. Far apart from one another
c. Both next to the F factor
d. Both oriented in the same direction
12. Greenhouse gases in the atmosphere absorb
a. More visible radiation than infrared
b. Visible and infrared equally
c. More infrared radiation than visible
d. Neither visible nor infrared radiation
13. Human red blood cells (RBCs) cannot be grown in culture because
a. The culture medium which supports the growth of RBCs has not been defined as yet
b. RBCs are extremely fragile
c. RBCs are terminally differentiated cells lacking nuclei
d. All of the above
14. How many different transfer RNA molecules are possible in a hypothetical organism where the ribosome detect a quadruplet instead of a triplet codon including the start and stop codon?
a. 64
b. 128
c. 20
d. 256
15. If a species contain 23% adenine in its DNA, then the percentage of guanine in its DNA would be:
a. 23
b. 46
c. 54
d. 27
16. During photosynthesis the source oxygen is:
a. Water
b. CO2
c. Glucose
d. Chlorophyll
17. How many molecules of dsDNA does a Drosophila cell nucleus contain?
a. 2 X 109
b. 46
c. 8
d. 0
18. A frame-shift mutation undergoes reversion to wild type. What are the ways in which reversion could occur?
a. Deletion of two bases
b. A missense mutation next to the original mutation
c. An inversion within the mutated gene
d. Insertion of two bases
19. If an affected male marries a normal female and produces affected daughters and sons in about the same number as unaffected daughters and sons, the trait is likely to be an
a. X linked dominant trait
b. Autosomal recessive trait
c. Autosomal dominant trait
d. X linked recessive trait
20. A biologist studied the environmental impact of a herbicide on squirrel reproduction. He selected two small islands with similar vegetation and similar size squirrel populations (about 200 squirrels) with equal reproductive rates. One island, selected at random, was sprayed with herbicide, and the other was used as a control. Squirrel reproduction rates were measured on both islands before and after the treatment. What is the greatest flaw in this investigation?
a. Lack of controls
b. Lack of replication
c. Lack of randomization
d. Lack of variables
Answer Key with Explanations
1. Ans. (b). The allele is recessive lethal
If the allele is a recessive lethal, there will not be the aa individuals in the population. In the question the percentage of aa individuals is given as 25%.
2. Ans. (c). Mostly females, with only single female being able to reproduce
Honey bee colony composed of:
(a). Queen: single queen, the only fertile female individual in the colony, laying egg is the man role
(b). Workers: the sterile female individuals, smallest individuals in the colony, constitute the majority of bees occupying the colony. Workers have specialized structures, such as brood food glands, scent glands, wax glands, and pollen baskets, which allow them to perform all the labors of the hive. They clean and polish the cells, feed the brood, care for the queen, remove debris, handle incoming nectar, build beeswax combs, guard the entrance, and air-condition and ventilate the hive during their initial few weeks as adults. Life span of worker bees is about 6 months in the summer
(c). Drones: They are the fertile male individuals in the colony. Very few numbers in the colony, only function is to mate with queen for fertilization.
3. Ans. (b). The process of capture and long-term storage of atmospheric oxygen
Carbon sequestration: The process of removing carbon from the atmosphere and depositing it in a reservoir. This is to avoid the dangerous effects of carbon dioxide in the environment.
4. Ans. (d). DNA double helix is a co-operative structure stabilized by hydrogen bonds and base pairing
5. Ans. (b). DNA looping
Enhancers are upstream or downstream regulatory sequence present in the well before the promoter region of DNA that binds to specific transcription factors to initiate transcription. In order to initiate transcription the enhancer along with transcription factors should interact with the promoter. Since enhancers are located far away from the promoter, the only possible way of interaction is by looping the DNA segment containing the enhancer region and come in contact with the promoter region.
6. Ans. (d). miRNA
miRNA: (micro RNA) They are small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression.
7. Ans. (c). Reptiles
Temperature dependent sex-determination: temperatures experienced during embryonic development determine the sex of the offspring. This condition is found in some reptiles.
8. Ans. (b). 1.43
9. Ans. (a). comparatively more permeable to K+ ions and nearly impermeable to Na+ ions
10. Ans. (b). Carbohydrates are added only to lipids on the lumen side of the ER and Golgi
11. Ans. (a). Close to one another
12. Ans. (c). More infrared radiation than visible
13. Ans. (c). RBCs are terminally differentiated cells lacking nuclei
14. Ans. (d). 256
The usual 64 codons are formed by 43 = 64, since codons are triplet
If the codons are quadruplet, we have four nucleotides; there will be 44 = 256 possibilities
15. Ans. (d). 27
Percentage of adenine = 23%
Since adenine base pair with thymine, the percentage of thymine is 23%
23 + 23 = 46% will be adenine and thymine
The rest (100 – 46) will be the percentage of guanine and cytosine, = 54%
Since guanine base pair with cytosine, there will be 54/2 percentage of guanine and cytosine in the DNA
Thus the correct answer is 54/2 = 27%
16. Ans. (a). Water
17. Ans. (c). 8
The diploid chromosome number (2n) of Drosophila is 8 (n = 4), each chromosome is a linear double stranded DNA in all eukaryotes, thus the total number of double stranded DNA in all eukaryotic cell will be the 2n chromosome number of that organism.
18. Ans. (d). Insertion of two bases
The frame shift mutation in the question is most probably due to the insertion of a nucleotide, it will create a shift in the reading frame. This change in reading frame was rectified by the second mutation where two nucleotides were inserted near to the first mutation. Thus with this, the first insertion and the second insertion of two nucleotides created an additional codon and this codon would code for an amino acid. More than that, the reading frame of the mRNA strand is regained with this insertion of additional two nucleotides.
19. Ans. (c). Autosomal dominant trait
20. Ans. (c). Lack of randomization