Final answer:
DNA ligase is the enzyme that joins Okazaki fragments during DNA replication, sealing breaks in the sugar-phosphate backbone to form a continuous DNA strand.
Step-by-step explanation:
The enzyme that joins Okazaki fragments by sealing breaks in the sugar-phosphate backbone of newly synthesized DNA is called DNA ligase. Okazaki fragments are short lengths of DNA that are synthesized on the lagging strand during DNA replication. They are named after the Japanese researchers, Reiji and Tsuneko Okazaki, who first discovered them. The synthesis of the lagging strand is discontinuous, meaning that the fragments are created separately and must be connected to form a continuous strand. After DNA polymerase I removes the RNA primers and replaces them with DNA nucleotides, DNA ligase comes into play to link the individual Okazaki fragments by creating phosphodiester linkages between them. This action effectively 'stitches' the newly formed strands of DNA into a single, continuous strand.