In Part A of our allele frequency simulation the population was not evolving so the population is said to be in equilibrium. • This means that allele frequencies for traits are relatively stable from one generation to the next in a population. • For this (no change in allele frequencies) to occur in a population, 5 conditions must be met. They are:
Random Mating: All members of a population have equal opportunity to produce offspring and thus an equal chance of passing on alleles. • Large Population • No movement in or out of a population: Individuals bring new alleles into the gene pool. • No mutation: Can introduce new alleles and change the relative frequency. • No natural selection: All of the genotypes must have an equal probability of survival, thus no phenotype can have an advantage.
When a population is in HWE do not significantly change from generation to generation. (no Evolution) • When a population IS NOT HWE the allele frequencies can change. (Evolution) • Are NATURAL populations ever likely to be IN HWE? • No. It would be difficult to control all 5 conditions. • Even in a controlled situation you cannot stop mutations!
In part B & C, not all individuals survived to reproduce. Which specific condition(s) of HWE was(were) not met in these simulations? Random mating Large population No movement in or out No mutation No natural selection
B.) In addition to the idea of equilibrium that Hardy and Weinberg proposed, they also came up with an equation that allows us to not only calculate allele frequencies but also predict frequencies!
http://anthro.palomar.edu/synthetic/synth_2.htm Godfrey Hardy(1877-1947) English Mathematician Wilhelm Weinberg(1862-1937) German Physician 1.) The Hardy-Weinberg Equation: p = dominant allele frequency q = recessive allele frequency p + q = 1 1 – q = p 1 – p = q p2 + 2pq + q2 = 1
3.) The Hardy-Weinberg Equation allows us to figure out genotype and allele frequencies. With this information, we can look at the change in allele frequencies over time in a population and gather numerical data on EVOLUTIONARY CHANGE!
Microevolution??? 1. In genetic terms: any change in the relative frequencies of alleles in a population’s gene pool over successive generations. • If allele frequencies change, then genotype frequencies change and we should SEE a change in phenotype in a population. • Ex: antibiotic resistance in a population of bacteria