Introduction: DNA dependent DNA polymerases are enzymes that are responsible for the replication of DNA. They catalyze the polymerization of nucleotides in a specific direction, which is important for the accurate replication of DNA.

Assertion: The DNA dependent DNA polymerases catalyze polymerisation only in one direction, that is 5'-3'.

Reason: The DNA polymerases on their own cannot initiate the process of replication.

Explanation:

DNA Polymerase: DNA polymerase is an enzyme involved in DNA replication. It catalyzes the addition of nucleotides to the growing DNA chain. There are several types of DNA polymerases, each with their specific function.

Directionality: DNA polymerases can only add nucleotides to the 3' end of a DNA strand. Therefore, the polymerization occurs in a specific direction, which is referred to as the 5'-3' direction.

Proofreading: DNA polymerases also have proofreading activity, which allows them to detect and correct errors made during replication. This helps to maintain the accuracy of the DNA sequence.

Initiation of Replication: While DNA polymerases are responsible for the replication of DNA, they cannot initiate the process on their own. Replication is initiated by the binding of specific proteins to the origin of replication, which then recruit DNA polymerases to the site.

Conclusion: DNA dependent DNA polymerases catalyze polymerisation only in one direction, that is 5'-3'. While they are responsible for the replication of DNA, they cannot initiate the process on their own. Replication is initiated by specific proteins that recruit DNA polymerases to the site.