This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Most Mobile DNA Consists of Transposable Elements”.
1. Pick the odd one out.
a) Introns
b) Cassettes
c) Jumping genes
d) Insertion sequences
View Answer
Explanation: Introns are intervening sequences found within the gene itself which divides the gene into several exons and are spliced off from the hnRNA to produce the intact mRNA. The rest, cassettes, jumping genes and insertion sequences are the different names for transposable elements and are short sequences of DNA that have the ability to move from one location to the other within the genome.
2. Transposable elements are often found once in a gene and have a unique sequence for its own.
a) True
b) False
View Answer
Explanation: Transposable elements have the ability to move from one location to the other within the genome and often make duplicate copies of them in this process. The process by which they are copied and inserted into a new site in the genome is called transposition.
3. Junk DNA are also a type of transposable element that can jump from one location to another within the genome.
a) True
b) False
View Answer
Explanation: Transposable elements are considered as selfish DNA that replicates but is of no use to the host cell. Defective selfish DNA which is no longer capable of either moving or expressing its gene is termed as junk DNA.
4. On the mechanism of the movement of transposable elements they are of ___________ types.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: On the mechanism of the movement of transposable elements they are of two types. They are transposons or type II elements and retrotransposons or type I elements.
5. The type of mutation that is imposed by transposons is ___________
a) Silent mutation
b) Reverse mutation
c) Polar mutation
d) Frame shift mutation
View Answer
Explanation: Transposable elements may contain transcription and/or translation termination signals. This blocks the expression of other genes downstream of the insertion site. This one-way mutational effect is known as polar mutation.
6. Transposons were first discovered in ___________
a) Rice
b) Bacteria
c) Mice
d) Maize
View Answer
Explanation: The first transposons were discovered in maize in 1948. For this discovery Barbara McClintock was awarded a Nobel Prize in 1983.
7. Transposons are able to move by ___________ mechanism(s).
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: Transposons can move by conservative or replicative process. In the conservative process the copy number of the transposons remains same but in replicative process the copy number increases.
8. The transposons are more abundant than retrotransposons in higher eukaryotes.
a) True
b) False
View Answer
Explanation: Transposable elements make upto 10% of higher eukaryotic genomes. Although retrotransposons are much more abundant in higher eukaryotes such as LINE, SINE, etc.
9. Silencing of transposons cannot be achieved by which of the following mechanisms?
a) RNAi
b) DNA methylation
c) DNA phosphorylation
d) Chromatin remodeling
View Answer
Explanation: As the movement of transposons can be destructive it is important to make the transposons silent to maintain the stability of the genome. They are kept inactive by epigenetic mechanisms such as RNA interference, DNA methylation and chromatin remodeling.
10. Pick the odd one out.
a) T4 phage
b) Mu phage
c) Coli phage
d) T2 phage
View Answer
Explanation: The Mu is an unusual E. coli bacteriophage. It is both a virus and a transposon. It is a temperate phage having both lytic and lysogenic growth cycles. It integrates into the bacterial genome by transpositional mechanism rather than site-specific recombination.
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