This set of Genetic Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Post-transcriptional Gene Silencing”.
1. If methods are based on cellular processes that lead to inactivation of gene expression by affecting the RNA, then it is called as ___________
a) transcriptional
b) pre-transcriptional
c) post-transcriptional
d) translational
View Answer
Explanation: If inactivation of gene expression is carried out by affecting the RNA then these methods are referred to as post-transcriptional. As transcription is the process of obtaining RNA from DNA.
2. Choose the incorrect statement for the method based on antisense RNA.
a) RNA is synthesized complementary to the sequence of the gene which is to be inactivated
b) It is achieved by placing a DNA sequence which encodes RNA complementary to the RNA to be inactivated
c) Expression of the endogenous gene is diminished
d) This method is preferred over gene disruption has gene inactivation can be achieved completely
View Answer
Explanation: Antisense RNA is the RNA which is complementary to the RNA sequence which is to be inactivated. It is done with the help of a DNA sequence. Expression of the endogenous gene is diminished. This method doesn’t lead to complete inactivation, which is not the case with gene disruption.
3. The method of post transcriptional gene silencing is particularly useful in ___________
a) plants
b) animals
c) insects
d) microorganisms
View Answer
Explanation: The method of post transcriptional gene silencing is particularly useful in plants.
4. Down regulation of expression of endogenous genes by transformation with constructs that would generate sense RNA, rather than anti-sense RNA is known as ___________
a) suppression
b) co-suppression
c) multisuppression
d) anti-suppression
View Answer
Explanation: When anti-sense RNA is used in plants, a phenomenon observed is co-suppression. It is the down regulation of expression of endogenous genes by transformation with constructs that would generate sense RNA, rather than anti-sense RNA.
5. In some organisms, presence of double stranded RNAs leads to breakdown of corresponding single stranded mRNA.
a) True
b) False
View Answer
Explanation: In some organisms, presence of double stranded RNAs leads to the breakdown of corresponding single stranded endogenous mRNA. The double stranded RNA is having one strand same as that of endogenous RNA.
6. Double stranded RNA is cleaved by a nuclease called as Dicer and small fragments are generated known as ___________
a) short interfering RNAs
b) long interfering RNAs
c) short interspersed RNAs
d) long interspersed RNAs
View Answer
Explanation: Double stranded RNA is cleaved by a nuclease called as Dicer and small fragments are generated, they are about 22 nucleotides long and are known as short interfering RNAs (siRNA).
7. The process of RNA inactivation by siRNAs is termed as ___________
a) RNA silencing
b) RNA interference
c) Short RNA inactivation
d) RNA disfunction
View Answer
Explanation: siRNAs are short interfering RNAs. The process of RNA inactivation by use of these is called as RNA interference (RNAi).
8. DNA _________ is also a method for gene silencing through short RNAs.
a) acetylation
b) phosphorylation
c) methylation
d) acylation
View Answer
Explanation: Short RNAs can also lead to gene silencing via DNA methylation.
9. siRNAs can either be introduced directly or by microinjection.
a) True
b) False
View Answer
Explanation: siRNAs can either be introduced directly or by microinjection. It can also be induced by feeding as in the case of C. elegans.
10. Introduction into host organism can also be done by using a DNA construct, which when transcribed, generates an RNA which is _________
a) circular
b) linear
c) double stranded
d) self-complementary
View Answer
Explanation: Introduction into the host organism can also be done by using a DNA construct, which when transcribed, generates a RNA which is self-complementary. It leads to the formation of double stranded RNA and is capable of activating RNAi effect.
Sanfoundry Global Education & Learning Series – Genetic Engineering.
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