![MCQs [2024]](https://engineeringinterviewquestions.com/wp-content/uploads/2021/02/Interview-Questions-2.png)
Gene Manipulation Multiple Choice Questions on “Site Directed Mutagenesis”.
1. Mutagens are physical or _________ agents.
A. Chemical
B. Mechanical
A. Hybrid
D. Exogenous
Answer: A
Clarification: Mutagens aid in the generation of mutants. These are chemical or physical agents that modify the organism’s DNA.
2. Site-directed mutagenesis is changing a given base in the cloned DNA.
A. True
B. False
Answer: A
Clarification: It is possible to change specifically any given base in a cloned DNA sequence. This technique is known as site-directed mutagenesis.
3. Creation of mutant proteins with novel properties is called ____________
A. Cloning
B. Protein engineering
A. Mutagenesis
D. Sequencing
Answer: B
Clarification: The technique of site-directed mutagenesis allows the creation of mutant proteins with novel properties, this is termed protein engineering.
4. When was the first method of site-directed mutagenesis developed?
A. 1940
B. 1970
A. 1980
D. 1950
Answer: C
Clarification: The first method of site-directed mutagenesis to be developed was the single primer method; developed by Gillam in 1980.
5. For single-primer method the DNA must be __________
A. Long
B. Short
A. Double-stranded
D. Single-stranded
Answer: D
Clarification: The method requires that the DNA to be mutated is available in a single stranded form, and cloning the gene in M13 based vectors makes this easy.
6. The synthetic oligonucleotide __________ the DNA synthesis.
A. Primes
B. Shortens
A. Lengthens
D. Degrades
Answer: A
Clarification: The synthetic oligonucleotide primes the DNA synthesis and is then later itself incorporated into the resulting heteroduplex molecule.
7. Clones can be screened using a _____________
A. PCR
B. Suppressor
A. Probe
D. Promoter
Answer: C
Clarification: The frequency with which mutated colonies arise, compared with wild-type colonies is low. In order to pick mutants, the clones can be screened by nucleic acid hybridization with P-32 labeled oligonucleotide as a probe.
8. The use of high-fidelity DNA polymerases has minimized the problem of ____________ mutations.
A. Internal
B. Site-directed
A. Extraneous
D. Point
Answer: C
Clarification: In earlier methods of mutagenesis, care had to be taken to avoid the introduction of adventitious changes. However, with high fidelity DNA, extraneous mutations can be avoided.
9. Contamination in heteroduplex molecules can be removed by __________________
A. Gel electrophoresis
B. PCR
A. Chromatography
D. Distillation
Answer: C
Clarification: The presence of contaminants reduces the proportion of mutant progeny, they can be removed by sucrose gradient centrifugation and gel electrophoresis.
10. The repair system of E.coli is ___________________
A. Lacking
B. Cysteine-directed
A. Methyl-directed
D. Mutated
Answer: C
Clarification: The major reason for low yield of mutant progeny is that the methyl-directed mismatch repair system of E. coli favors the repair of non-methylated DNA.
11. Which DNA are repaired at the site of mismatch?
A. Long
B. Short
A. Degraded
D. Unmethylated
Answer: D
Clarification: Newly synthesized DNA strands that have not yet been methylated are preferentially repaired at the position of mismatch.
12. Which of the following mutations are not used to overcome problems associated with the mismatch repair system?
A. MutL
B. MutS
A. MutH
D. MutE
Answer: D
Clarification: The problems associated with the mismatch repair system can be overcome by using host strains carrying mutL, muD, or mutH mutations.
13. The mutated strains mutL, mutS, and mutH prevent the methyl-directed repair of mismatches.
A. True
B. False
Answer: A
Clarification: The host strains carrying mutations mutL, mutS, and mutH prevent the methyl-directed repair of mismatches. They hence resolve the problems associated with the repair system.
14. All the primer extension methods of mutagenesis require _____________ template.
A. Double-stranded
B. Degraded
A. Single-stranded
D. RNA
Answer: C
Clarification: A disadvantage of all of the primer extension methods of mutagenesis is that they require a single stranded template.
15. Which kind of DNA are easier to prepare for PCR mutagenesis?
A. Linear
B. Circular
A. Single-stranded
D. Double-stranded
Answer: D
Clarification: With PCR-based mutagenesis, the template can be single-stranded or double-stranded, circular or linear. Double-stranded DNAs are easier to prepare.