Multiple Choice
What is the most likely consequence if DNA ligase is mutated and loses its function during DNA repair?
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17. Mutation, Repair, and Recombination
DNA Repair
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If DNA ligase was nonfunctional, what would be a likely consequence?
A
DNA polymerase would be unable to add nucleotides to the growing DNA strand.
B
Thymine dimers would accumulate due to failure in nucleotide excision repair.
C
The DNA double helix would not unwind during replication.
D
Okazaki fragments on the lagging strand would remain unjoined, leading to fragmented DNA.
Verified step by step guidance1
Understand the role of DNA ligase in DNA replication: DNA ligase is an enzyme responsible for joining Okazaki fragments on the lagging strand by forming phosphodiester bonds between adjacent nucleotides.
Recall that during replication, the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, which need to be connected to form a continuous strand.
Consider what happens if DNA ligase is nonfunctional: the Okazaki fragments cannot be joined together, resulting in fragmented DNA strands on the lagging strand.
Recognize that other processes such as nucleotide addition by DNA polymerase, unwinding of the DNA helix, and repair of thymine dimers are carried out by different enzymes and would not be directly affected by the absence of DNA ligase.
Conclude that the primary consequence of nonfunctional DNA ligase is the persistence of unjoined Okazaki fragments, leading to fragmented and incomplete DNA strands on the lagging strand.
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