Question

The Okazaki fragments in DNA chain growth
A. Results in transcription
B. Polymerise in the 3' to 5' direction and forms replication fork
C. Proves semi-conservative nature of DNA replication
D. Polymerise in the 5' to 3' direction and explain 3' to 5' DNA replication

Answer 1

The process of replication in living cells needs a set of enzymes. The main enzyme that takes part in replication is referred to as DNA-dependent DNA polymerase. It is highly efficient and it can polymerise some 2000 bp per second. Replication begins at a certain region of DNA which is called origin of replication. The vectors provide the origin of replication.

Complete answer:
The DNA dependent DNA polymerases catalysed polymerisation only in one direction, that is 5'to 3'. This creates some additional complications at the replication fork. As a result the replication is continuous on one template strand with polarity 3'to 5'. It is at this time known as leading daughter strand. The replication is discontinuous in the form of short Okazaki fragments on other template strands with polarity 5'to 3', this is known as lagging daughter strand. The discontinuously synthesised fragments are later joined by the enzyme DNA ligase.
Now let us know about given options:
Results in transcription :- the process of copying genetic material is termed as transcription from DNA into RNA . It occurs due to the principle of complementarity. It means formation of bonds between base pairs and not due to okazaki fragments .
Polymerise in the 3' to 5' direction and forms a replication fork :- replication fork is formed due to the unwinding of DNA molecule into two strands . Unwinding of parental molecules occurs due to the enzyme helicase .
Proves semi-conservative nature of DNA replication :- Matthew Meselson and Franklin proved semiconservative nature of DNA . The scheme told that two strands of DNA would separate and acts as a template for synthesis of new DNA.
Polymerise in the 5' to 3' direction and explain 3' to 5' DNA replication :- The replication is discontinuous in the form of short Okazaki fragments on other template strands with polarity 5'to 3', this is known as lagging daughter strand. Thus this option is correct.

Our required answer is (D) that is Polymerise in the 5' to 3' direction and explain 3' to 5' DNA replication.

Note: Watson and Crick proposed a scheme for showing DNA replication while proposing the double helical structure of DNA. The scheme suggested that the two strands would separate and act as a template for the synthesis of new complementary strands. After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand. This scheme was termed as semiconservative DNA replication.