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Why does synthesis of DNA proceed only in the $5^{'}$ to $3^{'}$ direction?
DNA polymerases can only add nucleotides to the $3^{'}$ end of a polynucleotide strand.
The $3^{'}$ end of the polynucleotide molecule is more electronegative than the $5^{'}$ end.
This is the direction in which the two strands of DNA unzip.
The chromosomes are always aligned in the $5^{'}$ to $3^{'}$ direction in the nucleus.

A

The

3^{'}

end of the polynucleotide molecule is more electronegative than the

5^{'}

end.

B

The chromosomes are always aligned in the

5^{'}

to

3^{'}

direction in the nucleus.

C

This is the direction in which the two strands of DNA unzip.

D

DNA polymerases can only add nucleotides to the

3^{'}

end of a polynucleotide strand.

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Solution

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DNA polymerase enzyme helps in the synthesis of DNA molecules from deoxyribonucleotides, the building blocks of DNA. They are essential for DNA replication and usually works in a pair to create identical DNA strands.
DNA polymerases require 3' OH group for the initiation of synthesis of DNA strand. Therefore, it can synthesize in only one direction by extending the 3' end of the pre-existing nucleotide chain. Hence, DNA polymerase moves along the template strand in 3' - 5' direction and the daughter strand is formed in a 5' - 3' direction.
So, the correct option is 'DNA polymerases can only add nucleotides to the 3′ end of a polynucleotide strand'.

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Q1

Why does synthesis of DNA proceed only in the

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Q2

DNA polymerase adds nucleotides to the 3’ end of a primer, extending the new chain in a 5’ → 3’ direction.

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Q3

Assertion :Synthesis of daughter or new strand occurs continuously along the parent 3

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Q4

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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Q5

Given below is the transcribed strand of the DNA duplex :3'-TACCGATCCGAGCTG-5'
(a)Draw the complementary DNA polynucleotide chain
(b)Construct the RNA molecule, which will'be transcribed.

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