MCQs on DNA Replication

 DNA replication occurs in all living organisms. It is an important biological process for inheritance. A DNA molecule replicates to form two identical copies of itself. During the cell cycle, replication occurs at ‘S’ phase. DNA replication is a semiconservative process, in the newly formed double-stranded DNA, one strand of original DNA is retained, which acts as a template for the formation of another strand. It is an enzyme catalysed process.

1. During replication, Okazaki fragments elongate

(a) leading strand towards the replication fork

(b) lagging strand towards the replication fork

(c) leading strand away from the replication fork

(d) lagging strand away from the replication fork

Answer: (d)

2. Which of the following enzymes separates the two strands of DNA during replication?

(a) Gyrase

(b) Topoisomerase

(c) Helicase

(d) DNA polymerase

Answer: (c)

3. DNA replication is

(a) conservative

(b) conservative and discontinuous

(c) semi-conservative and discontinuous

(d) semi-conservative and semi-discontinuous

Answer: (d)

4. Which of the following is used in DNA replication studies?

(a) Neurospora crassa

(b) Drosophila melanogaster

(c) Escherichia coli

(d) Pneumococcus

Answer: (c)

5. Which of the following helps in opening of DNA double helix in front of replication fork?

(a) topoisomerase

(b) DNA polymerase-I

(c) DNA gyrase

(d) DNA ligase

Answer: (c)

6. Termination of replication is triggered by

(a) DNA polymerase

(b) Helicase

(c) SSB

(d) Tus protein

Answer: (d)

7. DNA polymerase synthesizes

(a) DNA in 5’-3’ direction

(b) DNA in 3’-5’ direction

(c) mRNA in 3’-5’ direction

(d) mRNA in 5’-3’ direction

Answer: (a)

8. Association of histones H1 with nucleosome shows

(a) the occurrence of transcription

(b) the occurrence of replication

(c) exposed DNA double helix

(d) the condensation of DNA into chromatin fibre

Answer: (d)

9. The 3’ – 5’ phosphodiester linkage joins

(a) two DNA strands

(b) two nucleotides

(c) a nitrogenous base with pentose sugar

(d) two nucleosides

Answer: (b)

10. The fragments of DNA are joined together by which of the following enzymes?

(a) Endonuclease

(b) DNA polymerase

(c) Primase

(d) Ligase

Answer: (d)

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