Genetic Engineering Multiple Choice Questions 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
Answer: c
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
Answer: d
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
Answer: a
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
Answer: b
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
Answer: a
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
Answer: a
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
Answer: b
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
Answer: c
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