This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Gene Expression – Regulation and Silencing”.
1. When was it first discovered that RNA molecules are capable of catalyzing chemical reactions?
a) 1962
b) 1972
c) 1982
d) 1992
View Answer
Explanation: In the year 1982, Thomas Cech and colleagues at the University of Colorado first obtained the evidence of RNA molecules being capable of catalyzing chemical reactions.
2. The studies that led to discovery of posttranscriptional gene silencing phenomena were performed on ____________
a) petunia
b) sunflower
c) maize
d) wheat
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Explanation: The studies began in 1990 using petals of petunia flower plants, that ultimately led to the discovery of posttranscriptional gene silencing (PTGS).
3. The phenomenon of RNA interference was discovered using the organism ___________________
a) Mus musculus
b) Drosophila
c) C. elegans
d) Arabidopsis thaliana
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Explanation: In 1998 Andrew Fire of Carnegie Institute of Washington and Craig Mello of the University of Massachusetts and their colleagues conducted experiments on the nematode C. elegans which ultimately led to the discovery of RNAi phenomena.
4. RNA interference is evolved as a genetic immune system.
a) True
b) False
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Explanation: RNA interference (RNAi) is thought to have evolved as a type of genetic immune system, protecting the organism from unwanted foreign genetic material such as dsRNA, which is otherwise non-existent in cells.
5. Dicer converts double-stranded RNAs into _______________
a) snRNA
b) siRNA
c) mRNA
d) tRNA
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Explanation: Dicer is a type of ribonuclease that fragments double-stranded RNAs into smaller fragments called small interfering RNAs (siRNA).
6. Which family of proteins plays a key role in gene silencing pathways?
a) Globulin
b) Argonaute
c) Intein-containing proteins
d) Amino-acyl transferases
View Answer
Explanation: Argonaute proteins are components of the RNA induced silencing complex. This RISC is involved in RNAi and therefore involved in gene silencing.
7. RNA interference is not observed in vertebrates.
a) True
b) False
View Answer
Explanation: RNAi was first observed in nematode C.elegans. Since then many RNAi pathways were discovered in animals that involved RISc and Dicer protein molecules.
8. What takes place when siRNAs are used in place of dsRNA in mammalian cells?
a) gene knock-down
b) apoptosis
c) necrosis
d) aggregation
View Answer
Explanation: When small interfering RNA are used in place of double stranded RNA, gene knock-down takes place. Subsequently there is inhibition of specific protein synthesis encoded by an mRNA having the same nucleotide sequence as that of injected siRNA.
9. The first RNAi therapeutics was aimed at treating ______________________
a) muscular dystrophy
b) macular degeneration
c) multiple myeloma
d) neurodegeneration
View Answer
Explanation: The first test RNAi (RNA interference) therapeutics came against macular degeneration. It is a disease responsible for loss of vision in the elderly, characterized by overgrowth of blood vessels behind the retina.
10. Which of the following RNAs are highly conserved?
a) let-1
b) pet-1
c) let-7
d) pet-7
View Answer
Explanation: In 2000, it was shown that a 21-nucleotide RNA, let-7 present in small worms is highly conserved throughout evolution. Humans encode several RNAs identical to let-7.
11. Micro RNAs participate in ______________
a) posttranslational modification
b) posttranscriptional modification
c) chromatin remodeling
d) gene silencing
View Answer
Explanation: Micro RNAs (mi RNAs) are processed from the same machinery as small interfering RNAs (siRNAs) and play a role in posttranscriptional RNA silencing pathways.
12. Drosha is an ___________________
a) enzyme
b) micro RNA
c) messenger RNA
d) satellite DNA
View Answer
Explanation: Drosha is an enzyme that cleaves the primary transcript of miRNA. The primary transcript has a 5’ cap and poly(A) tail and is long, double-stranded, hairpin shaped RNA.
13. Which type of RNAs suppress the movement of transposons in the germline?
a) mRNAs
b) piRNAs
c) miRNAs
d) tRNAs
View Answer
Explanation: Piwi-interacting RNAs (piRNAs) are a distinct class of RNA molecules that prevent the movement of transposable elements in the germ cells. These RNAs associate with PIWI proteins, a subclass of Argonaute family.
14. PIWI proteins have been best studied in _________________
a) mice
b) fruit flies
c) nematodes
d) maize
View Answer
Explanation: PIWI proteins have been best studied in fruit flies, where their absence leads to defects in suppression of transposon movement in germ cells and incapability of forming gametes.
Sanfoundry Global Education & Learning Series – Cell Biology.
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