Question

Consider a cell with a mutation in the DNA ligase enzyme that renders DNA ligase non-functional. Assuming all other enzymes needed are functional, how much of DNA replication would be expected to occur?

Answer 1

In DNA replication, a non-functional DNA ligase caused by a mutation would lead to incomplete DNA strands due to the failure to join Okazaki fragments. Research by Reiji Okazaki on T4 phage mutants confirmed the role of DNA ligase in this process.

Step-by-step explanation:

In a cell where DNA ligase is non-functional due to a mutation, DNA replication would initiate normally, but the process would not be completed successfully because DNA ligase plays a critical role in the joining of Okazaki fragments during lagging strand synthesis. Without functioning DNA ligase, these fragments cannot be properly connected, leading to an accumulation of incomplete DNA strands. As DNA ligase is responsible for the final joining step in DNA repair and recombination as well as replication, its absence would lead to errors persisting in the DNA and possibly result in severe consequences for the cell.

The enzyme that is likely to be mutated when there is an impairment in the joining of Okazaki fragments during DNA replication is DNA ligase. This was highlighted by Reiji Okazaki's research on T4 phage mutants, which demonstrated that a deficient DNA ligase leads to the accumulation of these short DNA fragments, indicating its critical role in this process.