Final answer:
The enzyme responsible for joining Okazaki fragments is DNA Ligase, which ensures the continuous DNA strand formation on the lagging strand during DNA replication by sealing the nicks between adjacent fragments.
Step-by-step explanation:
The enzyme responsible for joining the Okazaki fragments together is DNA Ligase. During DNA replication, DNA ligase plays a crucial role in sealing the nicks between adjacent Okazaki fragments on the lagging strand, thus completing the synthesis of a continuous DNA strand.
When examining the replication fork, DNA Polymerase I functions by removing the RNA primers from the Okazaki fragments and replacing them with DNA nucleotides. Ultimately, it is DNA ligase that performs the final ligation step, effectively linking the separate fragments into a single, continuous DNA strand.
If a cell strain shows impaired joining of Okazaki fragments, a mutation in DNA ligase is the most suspected because it is this enzyme that is responsible for connecting the fragments.