Genetic Equilibrium Chapter 16- Section 1

What is a population? A group of individuals of the same species that routinely interbreed Population Genetics – the study of evolution from a genetic point of view Microevolution- the change in the collective genetic material of a population Biston betularia f. typica is the white- bodied form of the peppered moth Biston betularia f. carbonaria is the black- bodied form of the peppered moth.

Variation of Traits within a population Within a population, individuals will vary in observable traits Ex. Fish of a single species in a pond will vary in size Few fish are very short or very long

Causes of variation Variations influenced by environmental factors Ex. Amount or quality of food, sunlight, living space Variations in genotype 1. Mutation – a random change in a gene 2. Recombination – reshuffling of genes in a diploid 3. Random pairing of gametes – millions of sperm are produced, 1 gets to fuse with egg

The Gene Pool gene pool A population’s gene pool is the total of all genes in the population at any one time. If all members of a population are homozygous for a particular allele, then the allele is fixed in the gene pool.

The Hardy-Weinberg Theorem non-evolving population. Used to describe a non-evolving population. Natural populations are NOT expected to actually be in Hardy-Weinberg equilibrium Deviation from Hardy-Weinberg equilibrium results in evolution Understanding a non-evolving population, helps us to understand how evolution occurs *Genotype frequencies in a population tend to remain the same from generation to generation unless acted on by an outside source

Conditions of the H-W Theorem 1.Large population size - small populations can have chance fluctuations in allele frequencies (e.g., fire, storm). 2.No migration - immigrants can change the frequency of an allele by bringing in new alleles to a population. 3.No net mutations - if alleles change from one to another, this will change the frequency of those alleles

Conditions of the H-W Theorem 3.Random mating - if certain traits are more desirable, then individuals with those traits will be selected and this will not allow for random mixing of alleles. 4.No natural selection - if some individuals survive and reproduce at a higher rate than others, then their offspring will carry those genes and the frequency will change for the next generation.

Hardy-Weinberg Equilibrium The gene pool of a non-evolving population remains constant over multiple generations; i.e., the allele frequency does not change over generations of time. The Hardy-Weinberg Equation: 1.0 = p pq + q 2 where p 2 = frequency of AA genotype; 2 pq = frequency of Aa plus aA genotype; q 2 = frequency of aa genotype

Hardy-Weinberg Equilibrium Population of cats n= white and 84 black bb = white B_ = black Can we figure out the Allele frequencies of individuals BB and Bb?