AP BIOLOGY

Detailed explanation-1: -You isolate a cell strain in which the joining together of Okazaki fragments is impaired and suspect that a mutation has occurred in an enzyme found at the replication fork. Which enzyme is most likely to be mutated? Answer: Ligase, as this enzyme joins together Okazaki fragments.

Detailed explanation-2: -If the gene for helicase is mutated, what part of replication will be affected? At the replication fork, the events taking place are helicase action, binding of single-strand binding proteins, primer synthesis, and synthesis of new strands. If there is a mutated helicase gene, the replication fork will not be extended.

Detailed explanation-3: -In prokaryotic cells, polymerase III is the major replicative polymerase, functioning in the synthesis both of the leading strand of DNA and of Okazaki fragments by the extension of RNA primers.

Detailed explanation-4: -Okazaki fragments that are not ligated could cause double-strand-breaks, which cleaves the DNA.

Detailed explanation-5: -The last deoxyribonucleotide is joined by a different enzyme, DNA ligase, which uses one ATP to join the Okazaki fragment into the growing lagging strand.