Which of the following enzymes is used to join DNA fragments?

Explanation

DNA polymerase adds nucleotides to the three prime (3')-end of a DNA strand, one nucleotide at a time. So option A is incorrect. In DNA replication, ligase's job is to join together fragments of newly synthesized DNA to form a seamless strand. So option B is correct. Primase are enzymes that catalyze the synthesis of short RNA molecules used as primers for DNA polymerases. So option C is incorrect. Restriction endonucleases are enzymes that recognize DNA sequences, scan the sequence and cleave the fragment around or within that sequence. So option D is incorrect.