NEET Biology DNA Replication Multiple Choice Question And Answers

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DNA Replication MCQs for NEET

Question 1. The multiplication of DNA is called Punjab

  1. Translation
  2. Replication
  3. Transduction
  4. Transcription

Answer: 2. Replication

The formation of new DNA from old DNA is called replication of DNA or duplication of DNA or multiplication of DNA

Question 2. DNA replication is

  1. Conservative and discontinuous
  2. Semiconservative and semi-discontinuous
  3. Semiconservative and discontinuous
  4. Conservative

Answer: 2. Semiconservative and semi discontinuous.

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Replication of DNA is semiconservative, i.e. from one DNA molecule, two new DNA molecules are produced and in each new DNA molecule, one strand is the parental type and another is the newly formed type.

It is semi-discontinuous because one strand is formed in a discontinuous fashion. One of the strands in each molecule synthesized is parental and the other is new.

Question 3. DNA replication is semiconservative because

  1. Only one of the parent strands acts as a template
  2. Both the strands of the new molecule are synthesized de novo
  3. One of the strands in each molecule synthesized is parental and the other is new.
  4. The daughter strands synthesized are dispersive

Answer: 3. One of the strands in each molecule synthesized is parental and the other is new.

Replication of DNA is semiconservative, i.e. from one DNA molecule, two new DNA molecules are produced and in each new DNA molecule, one strand is parental type and another is newly formed type.

It is semi-discontinuous because one strand is formed in a discontinuous fashion. One of the strands in each molecule synthesized is parental and the other is new.

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Question 4. Semiconservative replication of DNA was first demonstrated in

  1. Streptococcus pneumoniae
  2. Salmonella typhimurium
  3. Drosophila melanogaster
  4. Escherichia coli

Answer: 4. Escherichia coli

Semiconservative replication of DNA was first demonstrated in E. coli. According to the semiconservative mode proposed by Waston and Crick, each strand of the two double helices formed would have one old and one new strand.

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NEET Biology DNA Replication Multiple Choice Question And Answers

Question 5. One of the following statements is wrong. Identify.

  1. DNA cannot produce its duplicate copies without the aid of RNA polymerase
  2. DNA helps in protein synthesis
  3. Rna produces complementary DNA
  4. DNA replication in e. Coli is conservative

Answer: 4. DNA replication in e. Coli is conservative

The statement in option 4 is wrong and can be corrected as DNA replication in E. coli is semiconservative.

Question 6. The type of centrifugation technique that can be used to differentiate heavy DNA from normal DNA is

  1. Agcl density gradient
  2. Ccscl density gradient
  3. Cscl density gradient
  4. Kcl density gradient

Answer: 3. Cscl density gradient

Heavy DNA can be separated from normal DNA by cesium chloride (CsCl) density gradient centrifugation.

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Question 7. Isotopes used for proving semiconservative replication of DNA are 13

  1. N14 and P13
  2. N14 and C14
  3. N14 and N15
  4. C14 and P31

Answer: 3. N14 and N15

Meselson and Stahl used 14 N and 15 N isotopes in their experiment to prove the semiconservative replication of DNA. 15N is not a radioactive isotope. It is a heavy isotope of 14N and can be separated from 14N by density gradient centrifugation

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Question 8. In Meselson and Stahl’s experiment, DNA extracted from the culture of one generation after the transfer from 15 n to 14n medium had a hybrid (or intermediate density).

Choose the correct reason.

  1. Since the generation time of e. Coli (culture) was about 20 minutes
  2. Since it would take 20 minutes for DNA translation
  3. Since it would take 20 minutes for the replication of DNA to RNA (transcription)
  4. Since it would take 20 minutes for the translation of RNA to protein

Answer: 1. Since the generation time of e. Coli (culture) was about 20 minutes

Option 1 is the correct reason. The replication time in E. coli is about 20 minutes.

The DNA was extracted after the interval of 20 minutes because by that time heavy 15N had been incorporated in the genetic material of E. coli and the resultant medium had a hybrid.

Question 9. Escherichia coli fully labeled with 15 n is allowed to grow in a 14n medium.

  1. The two strands of DNA molecule of the first-generation bacteria have
  2. Different densities and do not resemble parent DNA
  3. Different density, but resemble parent DNA
  4. Same density and resembles the parent DNA
  5. Same density, but does not resemble parent DNA

Answer: 1. The two strands of DNA molecule of the first-generation bacteria have

After one generation in a 14N medium, the 15N labeled DNA of bacteria would settle at a level intermediate between heavy and light bands due to semiconservative DNA replication.

Thus, it had a different density and did not resemble the parent DNA.

Question 10. If a completely radioactive double-stranded DNA molecule undergoes two rounds of replication in a non-radioactive medium, what will be the radioactive status of the four resulting molecules?

  1. Half the number contains no radioactivity
  2. All four still contain radioactivity
  3. Three out of four contain radioactivity
  4. Radioactivity is lost from all four

Answer: 1. Half the number contains no radioactivity

DNA replication is semiconservative, i.e. during each replication, one of the parental strands is retained and one new daughter strand is formed.

Thus, only half of the parental DNA molecule (non-radioactive) is carried to the next generation.

In the given situation, half the number of resulting molecules would contain radioactivity whereas the other half would not contain radioactivity.

Question 11. Escherichia coli with completely radioactive DNA, was allowed to replicate in the non-radioactive medium for two generations.

The percentage of bacteria with radioactive DNA is

  1. 50%
  2. 12.5%
  3. 100%
  4. 25%

Answer: 1. 50%

E. coli with completely radioactive DNA was allowed to replicate in the non-radioactive medium for two generations.

The percentage of bacteria with radioactive DNA is 50% because, in the first generation, 100% of bacteria will have one strand radioactive, but in the next generation, only 50% of bacteria will have one radioactive strand.

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Thus, 50% of the strands will be labeled, since DNA replication is semiconservative in nature.

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Question 12. In Meselson and Stahl’s experiment using e.coli culture, the duration between the appearance of equal amounts of light and heavy DNA was

  1. Two generations
  2. 40 Minutes
  3. 20 Minutes
  4. Three generations

Choose the correct option for a given statement of the question.

  1. 1 and 2
  2. 2 and 3
  3. 3 and 4
  4. 1 and 4

Answer: 1. 1 and 2

An equal amount of heavy DNA and light DNA was observed in the E. coli culture after the two generations. In forming two generations, E. coli needs about 40 minutes.

Question 13. DNA molecule with normal thymidine in both the strands was made to replicate in radioactive thymidine-rich media. After three replications what will be the number of DNA molecules with radioactive thymidine in both strands?

  1. 6
  2. 4
  3. Only 2
  4. 8

Answer: 3. Only 2

Because of the semiconservative method of DNA replication, only 2 molecules of DNA will have radioactive thymidine.

Question 14. Taylor conducted experiments to prove the semiconservative mode of chromosome replication on

  1. Vinca rosea
  2. Vicia faba
  3. Drosophila melanogaster
  4. E. Coli

Answer: 2. Vicia Faba

The semi-conservative mode of chromosome replication was proved by Taylor in Vicia faba.

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Question 15. The radioisotope used by Taylor was

  1. Iron
  2. Titanium
  3. 3H
  4. H3

Answer: 3. 3H

The semiconservative replication of DNA was demonstrated by Taylor et al. in 1957 with radioactive- H ( )3 H containing thymine instead of normal thymine.

Question 16. Which enzyme is required for the following process damp + atp → datp + amp?

  1. Polymerase
  2. Phosphorylase
  3. Phosphatase
  4. Pectinase

Answer: 2. Phosphorylase

The nucleotides present in the nucleoplasm in the form of monophosphates are activated into triphosphates in the presence of the enzyme phosphorylase.

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Question 17. Deoxyribonucleoside triphosphate serves dual purposes of

  1. Acting as substrate
  2. Acting as an enzyme
  3. Providing energy for polymerization
  4. Increasing the rate of reaction.

Choose the correct option.

  1. 1 and 2
  2. 2 and 3
  3. 3 and 4
  4. 1 and 3

Answer: 4. 1 and 3

The phosphorylated nucleotides are de ATP (deoxyadenosine triphosphate), deCTP(deoxycytidine triphosphate), and deTTP (deoxythymidine triphosphate). These triphosphates of bases serve dual purposes. They act as substrates as well as provide energy for the polymerization of nucleotides by releasing energy after dissociating the phosphate group. Thus, option 4 is correct

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Question 18. In the given options, identify the correct equation of DNA replication.

(DNA)n + dntp ↔ (DNA)n + 1ppi
(DNA)n + 1 + dntp ↔ (DNA)n + 1ppi
(DNA)n + 2 + dntp ↔ (DNA)n + 1ppi
(DNA)n + 1 + dntp ↔ (DNA)n + 2 + ppi
Answer: 1. (DNA)n + dntp ↔ (DNA)n + 1ppi

Question 19. Replication occurs within the small opening of the DNA helix called

  1. Replication fork
  2. Duplication fork
  3. DNA fork
  4. Rna fork

Answer: 1. Replication fork

During replication, the complete DNA strand does not open at one stretch due to a very high energy requirement.

The point of separation proceeds slowly in both directions. In each direction, it gives the appearance of a Y-shaped structure called a replication fork in which replication occurs.

Question 20. The definite region of DNA where replication begins is known as

  1. Origin of mutation
  2. Origin of nucleotide
  3. Origin of replication
  4. Replication site

Answer: 3. Origin of replication

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The definite region of DNA where replication begins is called the origin of replication. At the origin of replication, several enzymes like helicase, SSB, etc., are recruited to ensure replication.

Question 21. The unwinding of DNA is done by

  1. Topoisomerase
  2. Exonuclease
  3. Helicase
  4. Ligase

Answer: 3. Helicase

Helicases (unwindases) unwind the DNA helix and separate the two strands during DNA replication.

Question 22. The enzyme that breaks h2 bonds in DNA is

  1. Helicase
  2. Topoisomerase
  3. Ligase
  4. Polymerase

Answer: 1. Helicase

Enzyme helicase unwinds the DNA helix and unzips the two strands of DNA by breaking H 2 bonds between the two strands

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Question 23. The enzyme DNA polymerase was discovered by

  1. Kornberg
  2. Okazaki
  3. Watson and crick
  4. Stahl and season
  5. Jacob and Monod

Answer: 1. Kornberg

DNA polymerase-I (Pol-I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, it was the first known DNA polymerase (and the first known kind of polymerase).

It was initially characterized in E. coli and is ubiquitous in prokaryotes.

Question 24. How many types of DNA polymerase control DNA replication in eukaryotes?

  1. 2
  2. 3
  3. 4
  4. Only one type

Answer: 2. 3

In eukaryotes, three types of DNA polymerases contribute to DNA  replication. They are polymerase α, polymerase δ and polymerase ε.

Question 25. The number of DNA polymerases in prokaryotic DNA replication is

  1. One
  2. Two
  3. Three
  4. Five

Answer: 2. Two

In prokaryotes, replication is carried out by two types of DNA polymerases, viz. 1 and 3

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Question 26. The DNA polymerization rate of DNA polymerase is

  1. 3.9 × 107 bp
  2. 2000 Bp/s
  3. 4.6 × 106 bp
  4. 5000 Bp/s

Answer: 2. 2000 Bp/s

DNA replication is rapid. The replication of DNA of E. coli with 4.6 × 106bp requires 20 minutes. On average, the rate of polymerization of bases is 2000 bp per second in each direction.

Question 27. DNA polymerase is another name of

  1. DNA-dependent DNA polymerase
  2. DNA-dependent RNA polymerase
  3. Rna-dependent RNA polymerase
  4. Rna-dependent DNA polymerase

Answer: 1. DNA-dependent DNA polymerase

DNA polymerases are also called DNA-dependent DNA polymerases

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Question 28. The enzyme that reduces the tension during the unwinding of the DNA helix in front of the replication fork is

  1. Topoisomerase
  2. Helicase
  3. Ligase
  4. Polymerase
  5. Endonuclease

Answer: 1. Topoisomerase

The two strands of DNA are joined with the help of H-bonds between the strands. Topoisomerase-I is specialized to form nicks or breaks in the double helix and helps to separate the DNA strands. Thus, it reduces the tension in strands during the unwinding of the DNA helix

Question 29. Identify the protein that stabilizes the separated complementary strands.

  1. Ligase
  2. Ssbps
  3. DNA polymerase
  4. Dsbps

Answer: 2. Ssbps

Single Strand Binding Proteins (SSBPs) prevent the recoiling of separated strands and stabilize them.

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Question 30. The function of helix-destabilizing proteins is to

  1. Keep uncoiled strands of DNA apart
  2. Resist uncoiling of DNA under normal conditions
  3. Repair DNA molecules during replication
  4. Keep DNA helix tightly coiled

Answer: 1. Keep uncoiled strands of DNA apart

Helix-destabilizing proteins are any protein that binds to single-stranded regions of duplex DNA and thereby, causes the unwinding of the helix, e.g. helicase. Thus, it helps to keep uncoiled DNA strands far apart.

Question 31. In DNA replication, the primer is

  1. DNA primer
  2. Rna primer
  3. Both DNA and RNA
  4. None of the above

Answer: 2. Rna primer

In DNA replication, RNA primer is required to initiate polynucleotide synthesis which is then elongated by DNA polymerase.

Question 32. Rna primer is a must for the initiation of DNA duplication as it

  1. Adds nucleotides to the template strand
  2. Activates DNA polymerase
  3. Activates RNA polymerase
  4. Stops DNA duplication

Answer: 1. Adds nucleotides to the template strand

The RNA primer attaches itself at the end of the template strand and adds the new nucleotides to it.

To initiate the formation of a new strand on the template strand, DNA polymerase needs the presence of RNA primer (short RNA segment) because the former cannot initiate polynucleotide synthesis, but can elongate it.

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Question 33. …………… Help in the removal of Rna primers.

  1. DNA polymerase-1
  2. Rna polymerase-2
  3. DNA polymerase-2
  4. DNA polymerase-3

Answer: 1. DNA polymerase-1

RNA primers are removed by DNA polymerase-I. It also plays a role in the repair of DNA.

Question 34. Ligase enzyme functions in

  1. Denaturation of DNA
  2. Digestion of lipids
  3. Joining bits of DNA
  4. Joining two chromosomes

Answer: 3. Joining bits of DNA

DNA polymerases can only catalyze DNA synthesis in 5′ and 3′ directions.

On the complementary strand, replication is discontinuous, resulting in small DNA segments called Okazaki fragments, which are joined by ‘The DNA ligase enzyme.

Question 35. Protein helping in the opening of DNA double helix in the form of the replication fork is

  1. DNA gyrase
  2. DNA polymerase-1
  3. DNA ligase
  4. DNA primase

Answer: 1. DNA gyrase

DNA gyrase participates in the unwinding and relieving super-coiling of DNA helix in the form of a replication fork during replication. It is a type of topoisomerase-2 enzyme.

Question 36. The Okazaki fragments in DNA chain growth cbse

  1. Polymerise in the 3′- 5′ direction and forms replication fork
  2. Prove the semiconservative nature of DNA replication
  3. Polymerise in the 5′- 3′ direction and explain 3′-5′ DNA replication
  4. Result in transcription

Answer: 3. Polymerise in the 5′- 3′ direction and explain 3′-5′ DNA replication

Okazaki fragments are polymerized in a 5 3′− ′ direction by DNA polymerase enzyme. Their replication is carried out in 3 5′ ′- the direction of the template strand, away from the replication fork

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Question 37. The new strand synthesized in small pieces and then joined together during DNA replication is called

  1. Dead strand
  2. Lagging strand
  3. Leading stand
  4. All of these

Answer: 2. Lagging strand

In template strands with polarity 5′-3′, DNA polymerase is not able to synthesize new strands in the 3 5′ ′- direction.

This strand is the lagging strand and on this strand, synthesis takes place discontinuously in small pieces called Okazaki fragments.
These are later joined by DNA ligase.

Question 38. During DNA replication, Okazaki fragments are used to elongate

  1. The leading strand toward the replication fork
  2. The lagging strand towards the replication fork
  3. The leading strand away from the replication fork
  4. The lagging strand away from the replication fork

Answer: 4. The lagging strand away from the replication fork

Okazaki fragments synthesized on a 5′-3′ DNA template, join to form a lagging strand that grows in 3 5-′ ′ direction, away from the replication fork

Question 39. Consider the following statements.

The new DNA strand is synthesized by the addition of nucleotides at the 5′–oh group.
DNA synthesis occurs in the 5′-3′ direction.

Choose the correct option.

  1. Statement 1 is correct, but 2 is incorrect
  2. Statement 1 is incorrect, but 2 is correct
  3. Both statements 1 and 2 are correct
  4. Both statements 1 and 2 are incorrect

Answer: 2. Statement 1 is incorrect, but 2 is correct

The incorrect statement can be corrected as the Synthesis of a new DNA strand takes place by the addition of DNA nucleotides to the 3′ – OH group of the last ribonucleotide of the RNA primer.

This synthesis takes place in the 5′ and 3′ directions and is catalyzed by DNA polymerase.

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Question 40. During DNA replication, the term leading strand is applied to the one that replicates in

  1. 5′ → 3′ Direction discontinuously
  2. 3′ → 5′ Direction continuously
  3. 5′ → 3′ Direction continuously
  4. 3′ → 5′ Direction discontinuously

For long DNA molecules, the two strands of DNA cannot be separated in its entire length due to the requirement of

  1. Enzymes
  2. High energy
  3. RNA
  4. Phosphate and nucleotide

Answer: 3. RNA

When the double helix of DNA unwinds, DNA replication on one of the two strands (3′-5′ strand) can easily proceed continuously in the 5′-3′ direction. This is the leading strand

Question 42. Choose the sequence in which the following enzymes are used in DNA replication.

  1. Helicase
  2. Primase
  3. Ssbps
  4. DNA polymerase
  5. DNA ligase

Choose the correct option.

  1. 1 → 4 → 4 → 3 → 2
  2. 1 → 2 → 3 → 4 → 5
  3. 1 → 3 → 2 → 4 → 5
  4. 1 → 4 → 3 → 2 → 5

Answer: 3. 1 → 3 → 2 → 4 → 5

A helicase unwinds and splits the DNA. Thereafter, Single-Strand Binding Proteins (SSBPs) swiftly bind to the separated DNA, thus preventing the strands from reuniting.

A primase then generates an RNA primer which initiates the synthesis of DNA.

Question 43. Which one of the following correctly represents the manner of replication of DNA?

NEET Biology DNA Replication MCQs The manner of replication of DNA

Answer: 4.

NEET Biology DNA Replication MCQs The manner of replication of DNA 4

When the double helix of DNA unwinds, DNA replication on one of the two strands (3′-5′ strand) can easily proceed continuously in the 5′-3′ direction. This is the leading strand.

Question 44. Which of the following statements is incorrect?

  1. DNA replication is the process by which DNA makes a copy of itself during cell division
  2. The first step in DNA replication is to ‘unzip’ the double helix structure of the DNA molecule
  3. DNA replication occurs in all living organisms
  4. All of the above is incorrect

Answer: 1. DNA replication is the process by which DNA makes a copy of itself during cell division

The statement in option (a) is incorrect and can be corrected as DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule.

It occurs during the S-phase of the cell cycle. Rest statements are correct

Question 45. All of the following statements characterize DNA replication except

  1. The second DNA strand is in the form of Okazaki segments
  2. DNA is synthesised in 3′ to 5′ direction in one strand and 5′ to 3′ in another
  3. The growth of the DNA chain is discontinuous
  4. The overall growth of the DNA chain is bidirectional

Answer: 2. DNA is synthesised in 3′ to 5′ direction in one strand and 5′ to 3′ in another

All given statements characterize DNA replication except the statement in option

Because DNA polymerase synthesizes DNA in a 5′ to 3′ direction only because DNA polymerase acts on the 3′OH of the existing strand for adding free nucleotides.

Both the Okazaki fragments and leading strand are synthesized in a 5′- 3′ direction. The discontinuous assembly of lagging strands enables

Question 46. During the replication of a bacterial chromosome DNA synthesis starts from a replication origin site and RNA primers are involved
Is facilitated by telomerase

  1. Moves in one direction of the site
  2. Moves in a bidirectional way

Answer: 4. Moves in a bidirectional way

Replication begins at the ori or origin of replication and proceeds on both sides from the ori, i.e. it is bidirectional. Unidirectional replication is rare.

Question 47. E. Coli has only 4 6 10. × 6 Base pairs and completes the process of replication within 18 minutes, then the average rate of polymerization is approximately

  1. 2000 Bp/s
  2. 3000 Bp/s
  3. 4000 Bp/s
  4. 1000 Bp/s

Answer: 3. 4000 Bp/s

E. coli has 4 6 10. × 6 base pairs. It completes the replication process in about 18 to 20 minutes, i.e. 18 60× seconds. Rate of polymerization or approximately 4000 bp/sec Thus, the correct option is (c)

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