ICMR JRF Life Science Exam July 2016
(Practice Questions with Answer Key Part 4)
(1). What are zooxanthellae?
a. Deep sea dwelling brightly pigmented fish
b. Algae living in corals
c. A species of crab
d. Xanthomonas infected zooplankton
(2). Hemophilia A and Hemophilia B have nearly identical phenotypes, but they result from mutations in different gens on the X chromosome. This is an example of
a. Locus heterogeneity
b. Epistatic interaction
c. Double heterozygosity
d. Variable expressivity
(3). Natural killer cells can be detected in human peripheral blood using
a. Anti-cd3 antibody
b. Anti-cd25 antibody
c. Anti-cd69 antibody
d. Anti-cd16 antibody
(4). Balanced genetic polymorphism occurs when there is selection against
b. All genotypes
c. All homozygotes
d. Only homozygous recessive
(5). Xth nerve is an example of
a. Mixed cranial nerve
b. Sensory cranial nerve
c. Spinal nerve
d. Motor nerve
(6). Which of the following viruses is known for its antigenic variation?
c. Yellow fever
d. Japanese encephalitis
(7). Scrapie is caused by
a. Fungal protein
b. Bacterial protein
c. Plant lipoprotein
(8). Which of the following cells secrete E-selectins?
b. Endothelial cells
c. Microglial cells
d. Epithelial cells
(9). Which of the following can induce polyploidy?
(10). Deoxy position of doxyribose in DNA is at
a. 1st carbon
b. 3rd carbon
c. 2nd carbon
d. 5th carbon
(11). Which of the following non-coding RNAs is involved in RNA editing
a. Sn RNA
(12). Which of the following types of neurons is predominantly lost in narcolepsy?
(13). Areas of low productivity are termed as
(14). Organisms that are plankton in the juvenile stage, but nekton or benthos in the adult stage are called
(15). The zygote : endosperm : material tissue ratio in a well-developed seed is
a. 1 : 1 : 1
b. 2 : 1 : 2
c. 1 : 3 : 1
d. 1 : 2 : 1
Answer key and Explanations
1. Ans. (b). Algae living in corals
It is an example for a symbiotic interaction in a population.
Zoochlorellae and Zooxanthellae are unicellular microscopic algae that symbiotically live in the outer tissue of some sponges, coelenterates and mollusks. Algae are autotrophs and they can prepare food by photosynthesis. Algae obtain materials released by metabolism of host animals for their photosynthesis.
2. Ans. (a). Locus heterogeneity
Locus heterogeneity: trait caused by mutations in genes at different chromosomal loci.
Epistasis: a non-allelic interaction in which expression of one gene is influence by other gene. Two types of epistasis
(1) Dominant epistasis: a dominant allele of one gene masks the expression of either alleles of second gene
(2) Recessive epistasis: a recessive allele of one gene masks the expression of either alleles of second gene
Expressivity: the degree to which an individual express a particular genetic trait or its mutation.
3. Ans. (d). Anti-cd16 antibody
CD16 is an NK cell receptor. Other NK cell specific cell surface receptors are Ly49, NCR, and CD94:NKG2 heterodimer
4. Ans. (c), All homozygotes
Polymorphism: the occurrence of two or more distinct morphologically distinct forms of a same species. There are three mechanisms that can cause polymorphism in nature
(1). Genetic polymorphism: phenotypes are genetically different
(2). Conditional developmental strategy: different phenotypes due to difference in environmental conditions
(3). Mixed development strategy: phenotype are randomly assigned during development
Genetic polymorphism: Defined by Ford in 1940, the simultaneous occurrence in the same locality of two or more discontinuous forms in such proportions that the rarest of them cannot be maintained just by recurrent mutation or immigration.
Balanced polymorphism: a selective scenario in which a heterozygote for two alleles of a gene has an advantage over either of the homozyous states
5. Ans. (a). Mixed cranial nerve
Cranial nerve: each of the twelve pairs of nerves which arise directly from the brain, not from the spinal cord, and pass through separate apertures in the skull.
Cranial nerves of human are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
6. Ans. (b). Influenza
Antigenic variation: the phenomenon in which virus or bacteria alters their surface antigenic features in order to escape from the host immune system.
7. Ans. (d) Prion
Scrape is a neurodegenerative disease in sheep and goats caused by prions. It is a type of bovine spongiform encephalopathy (BSE)
Prions are the infective protein particles commonly called as PrP (prion protein).
8. Ans. (b). Endothelial cells
Selectins are cell adhesion molecules. There are several types of selection. All selectins are single chain trans-membrane glycoproteins. Selections are a type of lectins since they bind specifically to sugar molecules. There are three types of selections
(1). E-selectin: produced by endothelial cells
(2). L-selectin: produced by lymphocytes
(3). P-selectin: produced by platelets and endothelial cells
9. Ans. (b). Colchicine
Colchicine is an alkaloid extracted from a plant called Colchicum autumnale (Liliaceae). It is an important medicine used in the treatment of gout. Colchicine induces chromosome doubling in cells by a process called endo-reduplication.
Endo-reduplication: chromosome division without cell division, results in the doubling of chromosomes.
Colchicine induces endo-reduplication by inhibiting the spindle fibre formation during cell division. Colchicine inhibits microtubule polymerization by binding to tubulin proteins. Tubulin is the main constituent of microtubules. Thus colchicine is a mitotic poison and also a spindle poison; moreover it is an anticancer drug candidate.
10. Ans. (c). 2nd carbon
11. Ans. (c). gRNA
gRNA or guide RNAs are RNAs which guide the insertion or deletion of uridine residues into mitochondrial mRNAs of kinetoplastid protists (example: Trypanosoma). This process is called as RNA editing.
Kinetoplastids: a group of flagellated protists characterized by the presence of an organelle with a large massed DNA called kinetoplast.
12. Ans. (b). Orexinergic
13. Ans. (a). Oligotrophic
14. Ans. (a). Meroplankton
15. Ans. (d). 1 : 2 : 1
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