The Genome Pace-Maker Hypothesis: A DNA Based Synthesis of Genome Size, DNA Replication/Repair and Evolution pp. 175-222
Authors: (John Herrick, Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada)
Abstract: In eukaryotes, genome size is strongly correlated with generation time and the duration of the DNA synthetic phase (S phase) of the cell cycle, suggesting that genome size acts as a pace-maker that sets the rate of progression through S phase, and by extension, through the cell cycle. Why genome sizes vary from species to species is a fundamental question facing evolutionary biology. Many hypotheses have been advanced; but their explanations rely largely on correlations with life history traits, and do not address in detail fundamental cellular processes such as the organization and control of the DNA replication program during S phase. DNA damage occurs randomly in the genome and cells have evolved a robust DNA replication program that can adapt to and promote repair of randomly occurring DNA lesions. A critical feature of that program is the organization of the genome into gene rich euchromatin, which replicates early, and gene poor heterochromatin, which replicates late in S-phase. The following will explore the relationship between early and late replicating DNA with the hope of providing additional insights into the relationships between genome size variation, DNA replication and repair, and the rate of molecular evolution.