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Standard XII
Biology
Ori and Replication Fork
Question

What is the basis for the difference in the synthesis of the leading and lagging strand of DNA molecules?
  1. Origins of replication occur only at the 5' end of the molecule
  2. DNA ligase works only in the 3′→5′ direction
  3. Helicases and single-strand binding proteins work at the 5' end
  4. DNA polymerase can add new nucleotides only to the 3' end of the growing strand

A
Helicases and single-strand binding proteins work at the 5' end
B
Origins of replication occur only at the 5' end of the molecule
C
DNA ligase works only in the 3′→5′ direction
D
DNA polymerase can add new nucleotides only to the 3' end of the growing strand
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Solution
Verified by Toppr

The new DNA strand that grows continuously in the 5' to 3' direction is called the leading strand. The basis of the difference between the leading and lagging strand is that DNA polymerase can join new nucleotides only to the 3' end of the growing strand. Okazaki fragments are formed on the lagging strand and they are joined by the activity of DNA ligase.
So, the correct option is 'DNA polymerase can join new nucleotides only to the 3' end of the growing strand'.

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Similar Questions
Q1
Which among the following statements is/are correct?

Statement 1: In the double-stranded DNA, only one strand serves as a template for the duplication of the new DNA.

Statement 2: Leading strand is continuously synthesised in 5’-3’ direction and lagging strand is discontinuously synthesised in 3’-5’ direction.

Statement 3: DNA polymerase reads the template strand in 5’-3’ direction.

Statement 4: Replication proceeds only in 5’-3’ direction

Choose the correct option
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Q2
Assertion :Synthesis of daughter or new strand occurs continuously along the parent 3 → 5 strand. Reason: DNA polymerase can polymerise nucleotides in 3 → 5 direction on 5 → 3 strand.
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Q3
Consider these following sentences and choose the correct ones.
I. Each gene contains a specific promoter region and a leader sequence for guiding the beginning of transcription.
II. Only one strand for DNA, called template strand is copied by RNA polymerase this strand runs in 3′→5′ direction.
III. RNA polymerase adds complementary nucleotides forming single strand mRNA in 3′→5′ direction.
IV. Section of DNA that has been transcribed is rewound into its original configuration.
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Q4
Which of the following differences are incorrect between leading and lagging strands of DNA?
Leading strandLagging strand
(i)It does not require DNA ligase for its growthDNA ligase is required for joining Okazaki
(ii)Formation of leading strand is slowerFormation of lagging strand is quite rapid.
(iii)Its template opens in in 5 // 3 directionIts template opens in 3 // 5 direction.
(iv)Formation of leading strand begins immediately at the beginning of replication.Formation of lagging strand begins a bit later than that of leading strand

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Q5
What is the basis for the difference in the synthesis of the leading and lagging strand of DNA molecules?
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