The "Origin of replication" is responsible for initiating replication.

In DNA replication, the origin of replication is a specific DNA sequence where the process begins. It is a site where the enzymes and other proteins involved in replication bind and initiate the unwinding of the DNA double helix. Once the DNA strands are unwound, the replication machinery, including DNA polymerase, can begin synthesizing new DNA strands using the existing ones as templates.

The recognition sequence is a term often associated with restriction enzymes, which recognize specific DNA sequences and cleave the DNA at those sites, but it is not directly related to the initiation of DNA replication.

Exonucleases are enzymes involved in the removal of nucleotides from the ends of DNA molecules but are not responsible for the initiation of replication.

Therefore, the correct answer is the "Origin of replication."