Replication

Let's analyze each statement:

Option 1: The DNA-dependent DNA polymerase catalyses polymerization in one direction, that is, 3'→5'.

This is incorrect. DNA polymerase always adds nucleotides to the 3' end of the growing DNA strand, meaning it synthesizes in the 5'→3' direction, not 3'→5'.

Option 2: DNA-dependent RNA polymerase catalyses polymerization in one direction, that is 5'→3'.

This is incorrect. DNA-dependent RNA polymerase is involved in transcription (RNA synthesis), not DNA replication. DNA-dependent DNA polymerase is used for DNA replication. Also, while RNA polymerase works 5'->3', this is talking about DNA replication, not RNA transcription.

Option 3: The DNA-dependent DNA polymerase catalyses polymerization in 5'→3' as well as 3'→5' direction.

This is incorrect. DNA polymerase can only synthesize DNA in the 5'→3' direction. It cannot add nucleotides to the 5' end of a growing strand.

Option 4: The DNA-dependent DNA polymerase catalyses polymerization in the 5'→3' direction.

This is correct. DNA-dependent DNA polymerase is the enzyme responsible for DNA replication in E. coli. It adds nucleotides to the 3' end of the growing DNA strand, synthesizing in the 5'→3' direction.

Therefore, the correct statement is that DNA-dependent DNA polymerase catalyzes polymerization in the 5'→3' direction.