1. Deletion of which domain of ARS would give the least replication rate in eukaryotes?
a) A domain
b) B1 domain
c) B2 domain
d) B3 domain
Explanation: The 11bp ‘A domain’ is the primary functional area of the ARS. Mutation in this domain gives 0% functionality of ORC so lease replication. Other mutations also reduce replication rate but not to such extent.
2. Which subunit in MCM is not phosphorylated in MCM after initiation is triggered?
a) 1
b) 2
c) 3
d) 7
Explanation: MCM has 6 subunits numbered from 2 to 7. After initiation of replication is triggered all subunits other than 2 are phosphorylated.
3. MCM has 6 subunits numbered from 2 to 7. After initiation of replication is triggered all subunits other than 2 are phosphorylated.
a) ζ (zeta), η (eta)
b) η (eta), ) θ (theta)
c) θ (theta), κ (kappa)
d) κ (kappa),θ (theta)
Explanation: Eta introduces two random base against the lesion say AA or TT. However, it is very error prone and requires zeta to carry out the remaining replication. Kappa and theta also participate in repair but by other ways
4. We know that Beta clamp in bacteria has two subunits and takes the shape of a ring. Which of this will be characteristic of PCNA which is a beta clamp homologue for eukaryotes?
a) Two subunits forming ring
b) Three subunits forming ring
c) Four subunits forming figure 8 like structure
d) Four subunits forming a larger ring
Explanation: PCNA has three subunits but its structure is similar (ring) like two subunit beta clamp. Larger ring formation would be unreasonable as the basic structure of DNA is exactly the same for both prokaryotes and eukaryotes.
5. What is the function of RFC in eukaryotic replication?
a) Catalytic subunit
b) SSB
c) Clamp loader
d) Primase
Explanation: RFC or Replication Factor C is the eukaryotic homologue of clamp loader. It loads the PCNA clamp. Eukaryotic replication primer is formed by alpha polymerase while RPA acts as SSB.
6. Which protein mentioned below can reverse central dogma?
a) Ribosome
b) Restriction Endonuclease
c) Reverse Transcriptase
d) RNA Polymerase
Explanation: Reverse transcriptase helps in cDNA synthesis from RNA, which is opposite to the central dogma, where RNA is synthesized from DNA. Ribosome and RNA polymerases obey central dogma, while Restriction Endonuclease is unrelated as it simply cleaves DNA at a specific site.
7. The catalytic activity resides in which subunit of RNA polymerase?
a) β′ (156 kDa)
b) β (151 kDa)
c) α (37 kDa)
d) σ70 (70 kDa)
Explanation: β′ and β subunits are mainly associated with the transcription start site where β′ subunit mainly confers the catalytic activity. The sigma subunit provides specificity while alpha subunit interacts with regulatory proteins.
8. What is the direction in which the transcript produced by RNA polymerase grows?
a) 3’->5’ direction on 3’->5’ strand
b) 5’->3’ direction on 5’->3’ strand
c) 3’->5’ direction on 5’->3’ strand
d) 5’->3’ direction on 3’->5’ strand
Explanation: In the process of RNA synthesis there is a short phase of hybrid DNA-RNA formation. This is possible only when two strands are oppositely oriented. As 3’-OH is necessary for adding new nucleotides, RNA is synthesized from 5’->3’ direction, so the template must be 3’->5’ oriented.
9. In an experiment you use RNA polymerase without its sigma factor for transcription. What will be the result that you observe?
a) More transcription
b) Less transcription
c) More specific transcription
d) More random transcription
Explanation: Sigma subunit is responsible for recognizing the transcription start site. In its absence the RNA pol will transcribe at non-specific random sites. Sigma plays no role in the rate of transcription so there is no chance in transcription rate in its absence.
10. In an experiment you mutate the consensus sequence at the -10 box. You observe the rate of transcription reduces. Now you make complementary mutation to the sigma factor. What will you observe?
a) Further decrease in transcription rate
b) Increase in transcription rate
c) Original transcription rate
d) Increase in rate of random transcription
Explanation: Complementary mutation in sigma factor helps to restore its -10 box recognition capacity which restores normal transcription rate. However, to improve the rate further both the -10 and -35 box sequences should be made more like the consensus