Quiz 01-February-2024

Labmonk quiz, NET Life Science,

#1. A single-strand nick in the parental DNA helix just ahead of a replication fork causes the replication fork to break. Recovery from this calamity requires

DNA ligase

DNA ligase

DNA primase

DNA primase

site-specific recombination

site-specific recombination

homologous recombination

homologous recombination

#2. In gene regulation, open reading frame (ORF) implies

a series of triplet codons not interrupted by a stop codon.

a series of triplet codons not interrupted by a stop codon.

a series of triplet codons that begins with a start codon and ends with a stop codon.

a series of triplet codons that begins with a start codon and ends with a stop codon.

intervening nucleotide sequence in between two genes.

intervening nucleotide sequence in between two genes.

the exonic sequence of a gene that corresponds to the 5′-UTR of the mRNA and thus does not code for the protein.

the exonic sequence of a gene that corresponds to the 5′-UTR of the mRNA and thus does not code for the protein.

#3. Pre-mRNAs are rapidly bound by snRNPs which carry out dual steps of RNA splicing, that removes the intron and joins the upstream and downstream exons. The following statements describe some facts related to this event: P. Almost all introns begin with GU and end with AG sequences and hence all the GU or AG sequences are spliced out of RNA. Q. U2 RNA recognizes important sequences at the 3′ acceptor end of the intron. R. The spliceosome uses ATP to carry out accurate removal of intron. S. An unusual linkage with 2′ OH group of guanosine within the intron form a ‘lariat’ structure. Which of the following combinations is correct?

S and P

S and P

Q and R

Q and R

P and Q

P and Q

R and S

R and S

#4. Synthesis of normal haemoglobin requires coordinated synthesis of α-globin and β-globin. Thalassemias are genetic defects perturbed in this coordinated synthesis. Patients suffering from deficiency of β-globin chains (β–thalassemia) could also be due to mutations affecting the biosynthesis of β-globin mRNA. The following statements describe the genesis of non-functional β-globin leading to β-thalassemia. P. Mutation in the promoter region of the β-globin gene. Q. Mutation in the splice junction of the β-globin gene. R. Mutation in the intron I of the β-globin gene. S. Mutations towards the 3′ end of the β-globin gene that codes for polyadenylation site. Which of the following combinations is correct?

P, Q and S

P, Q and S

P, Q and R

P, Q and R

R, S and P

R, S and P

Q, R and S

Q, R and S

#5. α-amanitin inhibits

only RNA polymerase II

only RNA polymerase II

only RNA polymerase I

only RNA polymerase I

only RNA polymerase III

only RNA polymerase III

#6. Bacteriophage λ has two modes in its life cycle, lytic and lysogenic. In the lysogenic mode, the expression of all the phage genes are repressed while the expression of repressor gene switches between on and off position depending on the concentration of repressor. The following statements are made: P. Repressor may act both as a positive regulator and a negative regulator. Q. Expression of repressor gene, cI is independent of the expression of cII and cIII genes. R. Mutation of cI gene will cause it to form clear plaques on both wild type E. coli and E. coli (λ+). S. Mutation at operators, OL and OR will allow the phage to act as a virulent phage. The correct statements are

P and Q

P and Q

R and S

R and S

Q and R

Q and R

S and P

S and P

#7. Amino acid selenocysteine (Sec) is incorporated into polypeptide chain during translation by

charging of Sec into tRNAser and then incorporation through selenocysteine codon.

charging of Sec into tRNAser and then incorporation through selenocysteine codon.

charging of serine into tRNAsec, modifi cation of serine into selenocysteine and then incorporation through a specially placed stop codon.

charging of serine into tRNAsec, modifi cation of serine into selenocysteine and then incorporation through a specially placed stop codon.

charging of serine into tRNAser followed by modifi cation of serine into selenocysteine and then incorporation through serine codon.

charging of serine into tRNAser followed by modifi cation of serine into selenocysteine and then incorporation through serine codon.

charging of Sec into tRNAser followed by incorporation through serine codon.

charging of Sec into tRNAser followed by incorporation through serine codon.

#8. Reverse transcriptase has both ribonuclease and polymerase activities. Ribonuclease activity is required for

the synthesis of new DNA strand

the synthesis of new DNA strand

the synthesis of new RNA strand

the synthesis of new RNA strand

the degradation of RNA strand

the degradation of RNA strand

the degradation of DNA strand

the degradation of DNA strand

#9. The bacterial flagellar motor is a multi-protein complex. Rotation of the flagellum requires movement of protons across the membrane facilitated by a multi-protein complex. The flagellar motor proteins combine to create a proton channel that drives mechanical rotation. In a screen for mutants, some non-motile ones were selected. These could have

mutations in the charged residues lining the ridge of the FliG subunit.

mutations in the charged residues lining the ridge of the FliG subunit.

mutations in tubulin and actin proteins.

mutations in tubulin and actin proteins.

mutated H+–ATPase.

mutated H+–ATPase.

mutations in kinesin proteins.

mutations in kinesin proteins.

#10. While replicating DNA, the rate of misincorporation by DNA polymerase is 1 in 105 nucleotides. However, the actual error rate in the replicated DNA is 1 in 109 nucleotides incorporated. This is achieved mainly due to

termination of DNA polymerase at mis-incorporated sites.

termination of DNA polymerase at mis-incorporated sites.

spontaneous excision of mis-incorporated nucleotides.

spontaneous excision of mis-incorporated nucleotides.

3′ → 5′ proofreading activity of DNA polymerase.

3′ → 5′ proofreading activity of DNA polymerase.

5′ → 3′ proofreading activity.

5′ → 3′ proofreading activity.

Finish

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