BIO 115 Lecture Notes - Lecture 30: Meiosis, Genome Size, Molecular Clock
Document Summary
Motoo kimura (1968): most evolution at the molecular level is neutral (due to drift) Neutral substitutions should accrue in a clock-like fashion. Different types of dna should evolve at different rates. Used to determine time based on base-pair substitutions, use the rates of molecular change to deduce the divergence time between two lineages in a phylogeny, can be calibrated with fossils for best results. Allow scientists to estimate the age of common ancestors by comparing the mutations in the same genomic context across a group of organisms. A molecular clock approach dates the origin of hiv in humans. Consumption of bush-meat that allowed hiv to enter. Faster evolution than synonymous sites indicates positive selection. Slower evolution than synonymous sites indicates purifying selection. Positive selection: accumulation of non-syn mutations in a coding region. Clusters of non-syn mutations leading up to humans. Key concepts substitution predicted under drift alone. The neutral theory of molecular evolution describes patterns of nucleotide.
