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The Okazaki fragments in DNA chain growth
A
polymerize in the $3'$-to-$5'$ direction and form the replication fork
B
prove the semi-conservative nature of DNA replication
C
polymerize in the $5'$-to-$3'$ direction and explain $3'$-to-$5'$ DNA replication
D
result in transcription
Detailed Solution
DNA polymerase can add nucleotides only in the $5' \rightarrow 3'$ direction.
The two template strands are antiparallel. On the template with $3' \rightarrow 5'$ polarity, synthesis is continuous (leading strand).
On the other template, with $5' \rightarrow 3'$ polarity, the new strand cannot grow continuously towards the fork. It is synthesised as short pieces called Okazaki fragments, each made in the $5' \rightarrow 3'$ direction.
These fragments are later joined by the enzyme DNA ligase after the RNA primers are replaced by deoxyribonucleotides; together they form the lagging strand.
Each fragment grows $5' \rightarrow 3'$, but the lagging strand as a whole appears to grow in the $3' \rightarrow 5'$ direction. In this way the Okazaki fragments explain the apparent $3'$-to-$5'$ DNA replication.
The semi-conservative nature of replication was proved by Meselson and Stahl, and Okazaki fragments have nothing to do with transcription.
So Okazaki fragments polymerize in the $5'$-to-$3'$ direction and explain $3'$-to-$5'$ DNA replication.
The two template strands are antiparallel. On the template with $3' \rightarrow 5'$ polarity, synthesis is continuous (leading strand).
On the other template, with $5' \rightarrow 3'$ polarity, the new strand cannot grow continuously towards the fork. It is synthesised as short pieces called Okazaki fragments, each made in the $5' \rightarrow 3'$ direction.
These fragments are later joined by the enzyme DNA ligase after the RNA primers are replaced by deoxyribonucleotides; together they form the lagging strand.
Each fragment grows $5' \rightarrow 3'$, but the lagging strand as a whole appears to grow in the $3' \rightarrow 5'$ direction. In this way the Okazaki fragments explain the apparent $3'$-to-$5'$ DNA replication.
The semi-conservative nature of replication was proved by Meselson and Stahl, and Okazaki fragments have nothing to do with transcription.
So Okazaki fragments polymerize in the $5'$-to-$3'$ direction and explain $3'$-to-$5'$ DNA replication.