Hardy-Weinberg and Mendel’sLaw 3rd time’s a charm
Mendelian Genetics Definitions • Allele - one alternative form of a given allelic pair • Allelic pair - the combination of two alleles in the gene pair • Homozygote - an individual which contains only one allele at the allelic pair • Heterozygote - an individual which contains one of each member of the gene pair • Genotype - the specific allelic combination for a certain gene or set of genes
Mendel's First Law • During gamete formation each member of the allelic pair separates from the other member to form the genetic constitution of the gamete
Mendel’sSecondLaw • Dihybrid cross - a cross between two parents that differ by two pairs of alleles (AABB x aabb). • During gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair.
Mendel’sLaw of Dominance • In a cross of parents that are pure for contrasting traits: • Only one form of the trait will appear in the next generation. • Offspring that are hybrid for a trait will have only the dominant trait in the phenotype. • Dominant and recessivetraits.
Hardy-Weinberg • The genetic pool in a population will remain constant from one generation to the next in the absence of disturbing factors. • When mating is random in a large population: • with no disruptive circumstances • the law predicts that both genotype and allele frequencies will remain constant because they are in equilibrium.
Hardy-Weinberg • mutations: introducing new alleles into a population • natural selection: changes in gene frequencies • nonrandom mating • genetic drift: allele frequencies grow higher or lower by chance • gene flow: mating between two populations transfers new alleles into a population.