A molecular biologist purified what she thought were all factors essential for DNA replication in order to set up an in vitro DNA replication system. When she tested the in vitro system, replication occurred. But, when she isolated the newly synthesized double-stranded DNA, denatured the DNA, and electrophoresed the single-stranded products, she noted that there were not only some long strands but also numerous short segments of DNA a few hundred nucleotides long. What was probably missing from the in vitro replication system she developed?

Question

Quizplus · Accepted Answer

The presence of numerous short segments of DNA a few hundred nucleotides long, even after replication, suggests that the in vitro system was missing DNA ligase. DNA ligase is responsible for joining the Okazaki fragments on the lagging strand to form a continuous DNA strand. Without DNA ligase, the newly synthesized DNA would remain in pieces, as observed.

A Molecular Biologist Purified What She Thought Were All Factors