The DNA polymerases and editing enzymes replicate the genome at a blazing speed with an amazing and near-perfect accuracy. The machinery that is responsible for genome duplication introduces one error for every 100 million nucleotides that

it copies (10-8 error per base pair for the mammalian genome).2-4 This error rate translates into approximately 30 new DNA variants in each offspring (de Inhibitors,research,lifescience,medical novo variants, as they are absent in the parents’ genomes).2-4 Given that the human species has evolved over 3.7 to 6.6 million years5 and over billions of meiotic divisions (genome duplications), and in view of the introduction of approximately 30 de novo variants per meiosis, Inhibitors,research,lifescience,medical one might surmise the enormous diversity of the human genome. Introduction of the new DNA

sequence variants (DSVs) throughout the evolution of humans has followed the population growth. The rapid expansion of the human population during the last 10,000 years, about 400 generations, has ultimately introduced a very large number of DSVs into the population genome.6 Consequently, the vast majority of DSVs in the population genome are relatively new. These new variants, having had an inadequate time to spread among the population compared to older variants, are less common and often rare. Likewise, the new variants have not had adequate exposure to evolutionary Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical selection pressure or a population drift; therefore, they generally are expected to exert SRT1720 in vitro larger biological effects. This is in contrast to ancient DSVs, which have had the chance to spread out and be subjected to selection pressure. Consequently, ancient variants are typically common and have small and often clinically negligible effects, as those

with large effect sizes are typically eliminated over years Inhibitors,research,lifescience,medical of evolution. The Plethora of DSVs in an Individual Genome/Exome Each genome contains approximately 3.2 billion nucleotides, of which approximately 4 million nucleotides are variants as compared to the reference genome. Therefore, each individual has a variant nucleotide for every 800 nucleotides in the genome. With the current population level, every nucleotide is expected to be polymorphic even though the vast majority of such variants are rare due to their very modern origins.6, 7 Since de novo variants are introduced in each offspring, no two individuals, with the exception of monozygotic twins, are genetically identical at the DNA sequence level. This diversity also extends to each individual: because of the error rate of the DNA replication machinery and replication of certain cells, the replicating cells in an individual are a genetic mosaic. Of the approximately 4 million DSVs in each genome, about 3.5 million involve only a single nucleotide and hence are called single nucleotide variants (SNVs) or single nucleotide polymorphisms (SNPs).