This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “DNA Repair”.
1. The correction of changes in DNA by a set of process known as___________
b) DNA repair
Explanation: DNA repair is the correction process which is used to maintain genetic stability.
2. The genome can maintain its essential cellular function even without DNA repair.
Explanation: Genome cannot maintain its essential cellular function if the DNA is damaged. So, for the accurate functioning, a set of correction processes are used known as DNA repair.
3. Name the repair system for UV mediated damage of DNA?
a) Exchange of homologous segments
b) DNA glycosylase
c) Nucleotide excision repair
Explanation: Exposure to UV radiation can cause pyrimidine dimer which is repaired by a light dependent direct system called photoreactivation.
4. Which of the following enzyme is used in photoreactivation process?
a) DNA ligase
b) DNA photolyase
c) DNA polymerase
Explanation: DNA photolyase participates in the DNA repair system when the damage takes place by UV radiation.
5. Name the repair system which involves the removal of the damaged segment of DNA?
a) Recombinational repair
b) Direct repair
c) Excision repair
d) Mismatched repair
Explanation: Excision of the damaged site comes under the excision repair system. It is of two types, base excision repair and nucleotide excision repair.
6. Name the enzyme which initiates base excision repair process?
a) RNA polymerase
b) DNA polymerase
c) DNA photolyase
d) DNA glycosylase
Explanation: DNA glycosylase cleaves N-glycosidic bonds which liberates altered base and generates apurinic or an apyrimidic site.
7. Which of the following enzyme works in the nucleotide excision repair?
a) DNA photolyase
b) ABC exinuclease
c) DNA glycosylase
Explanation: ABC excinuclease involves the removal of short, usually 12 nucleotide segment. This system is best studied in E.coli.
8. Mark the one, which is NOT a subunit of ABC exinuclease?
Explanation: ABC exinuclease binds at the site of lesion for the purpose of excision. It consists of three subunits i.e, UvrA, UvrB, and UvrC.
9. Which of the following is NOT the function of the enzyme systems involved in mismatch repair?
a) Recognize mismatched base pair
b) Gene conversion
c) Determine incorrect base from a mismatch
d) Excise incorrect base and carry out repair system
Explanation: Gene conversion is the phenomenon of changing allele forms during recombination and DNA repair.
10. Mark the one, which is CORRECT for SOS repair.
a) RecA protein participates
b) A free radical mechanism is involved
c) The repair enzyme functions only once
d) No bases or nucleotides are removed
Explanation: SOS repair involves RecA protein and is responsible for error prone replication. Final reaction is catalyzed by DNA ligase.
Sanfoundry Global Education & Learning Series – Life Sciences.
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