First Advisor

Justin Courcelle

Date of Publication

Spring 6-5-2018

Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Biology






DNA replication -- Research, Chromosome replication, Mutation (Biology)



Physical Description

1 online resource (vii, 165 pages)


To maintain genomic integrity, all cells must accurately duplicate their genetic material in order to provide intact and complete copies to each daughter cell following cell division. Successful inheritance of chromosomal information without changing even a single nucleotide requires accurate and robust DNA replication. This requires that cells tightly control replication initiation from the origin(s), processive elongation of the replisome, and the completion of DNA replication by resolving convergent replication forks ensuring that each sequence is duplicated without alteration. Unlike initiation and elongation, the process by which replication forks converge and are resolved into two discrete, inheritable DNA molecules is not well understood. This process must be remarkably efficient, occurring thousands of times per cell division in human cells, and is likely to be a fundamental step in regulating genome stability in all cells.

In this dissertation I address how DNA replication completes in the model system Escherichia coli. To achieve this, I examined candidate mutants for impairments in the completion of DNA replication. By evaluating growth, viability, chromosomal copy number, and plasmid stability I identified a requirement for the proteins RecBCD, ExoI, and SbcCD in the completion reaction. SbcCD and ExoI act before RecBCD in the completion reaction and process the DNA intermediates arising as replication forks converge. These enzymes act in the completion reaction without recombination or RecA, but in the absence of the normal process recombination is required to complete DNA replication via an aberrant pathway that results in genomic instability.


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