BIOL 304 Lecture Notes - Lecture 22: Alternate History, Molecular Clock, Genetic Drift
Document Summary
Sequence divergence (number of nucleotide change/total nucleotides: chances that a homologous locus have different substitution) Amount of divergence and rate of divergence are used to infer relatedness of species. Use a calibrated divergence point and a observed divergence. Fossil record is biased (we don"t know if it"s the real earliest ancestor, underestimate the divergence) Some lineages do not diverge at a uniform rate synonymous divergence are not very clock like (opposed by selection) Small population and fluctuating population have more drift. Core genome: a small group of genes encoding proteins whose structure cannot be altered without severely disabling the organism. Redundancy of genome allows alternative metabolic pathway in case of loss of function mutation; also an evolved character itself. Slightly deleterious mutations can remain in genome for a while and accumulate; lineages don"t die immediately. When genes are not selected, they can slowly decay. Will be eliminated because of metabolic burden to replicate.
