BISC 102 Chapter Notes - Chapter 24, 25, 27: Allele Frequency, Rifampicin, Genetic Distance
19 Jan 2018
School
Department
Course
Professor
Document Summary
24. 4 - evolution in action: recent research on natural selection. Patient had 1 or few cells where rpob gene had c--->t mutation before drug therapy. Normal conditions: common form or rna polymerase work better than mutant forms. Cells with c--->t has advantage in new environment. : mutation led to resistant and nonresistant strains of tb. : variation in phenotypes of two strains (drug susceptibility, dry resistance) due to variation in genotypes. : little m. tuberculosis cells survived first round antibiotics to reproduce. Cells with drug-resistant allele had higher reproductive success. Natural selection acts on individuals bc individuals have diff reproductive success. Only populations evolve; allele frequencies change in populations. Directional selection: avg phenotype of population changed in 1d. Stabilizing selection: selection greatly reduces 1 extreme in range of phenotypes; selection reduces opposite extreme. No change in avg value of trait over time. Disruptive selection: eliminates phenotypes near avg value, favours extreme phenotypes. Overall amount of genetic variation in population maintained.
