Microevolution I Variation A Phenotypic 1 Either or 2 Vary in gradation along a continuum a Height in humans i influence of two or more genes B Genetic 1 Differences among individuals in gene DNA composition a Sources i Mutations ii Alterations in chromosome structure iii Rapid Reproduction II Population A Group of potentially sexually interbreeding organisms of the same species living in the same area at the same time B Population Genetics 1 Study of genetic variability in populations and evolutionary forces C Allele One of two or more alternate forms of a gene 1 Located in the loci 2 Gene Pool All the alleles of all the genes in a population at any one time 3 In diploid each locus is present twice because homologous chromosomes 4 Fixed Allele All individuals are homozygous for the same allele Little a little a on both loci 5 Allele frequency The proportion of a specific allele in a particular population Each allele is going to have a relative frequency Not altered by process of inheritance alone a Remain constant unless acted upon outside agents b any changes in allele frequency is microevolution i Microevolution Small shift of recessive allele frequencies over generations a 500 plants 320 are homozygous dominant red AA 160 are heterozygous red Aa 20 homozygous rec red aa 64 AA 32 Aa 4 aa How many alleles are in population at this locus 1 000 500x 2 alleles What are the allele frequencies Make table with Aa 640 for AA for A 160 AA and 160 aa for Aa Aa is 40 little a Freq A 0 8 freq a 0 2 1 0 has to equal 1 for 100 What will be allele frequency of A and a in the next generation Cross between 8A and 2a w 8A and 2a get 64AA 16Aa 16Aa 04 aa same as parent generation b Genetic equilibrium the allele frequency and genotype frequency do not change from generation to generation in a population i Population not undergoing evolutionary change III Hardy Weinberg Principle changes in allele frequencies A If a population is large then the process of inheritance by itself does not cause B Explains why dominant alleles not necessarily more common than recessive alleles C Describes genetics of populations that aren t evolving genetic equilibrium 1 Not a typical situation 2 Important because it provides a base line so that when we see allele frequencies do change we can figure out evolutionary forces acting upon population that make it change D HW Equilibrium Populations frequencies of alleles and genotypes will remain 1 As long as pop mates randomly and not acted upon by outside agent then it 2 HW Equation calculate allele and gene frequencies and expected frequency a p frequency of dominant allele in pop q frequency of recessive allele b Parent generation frequency A 0 7 frequency a 0 3 What will be p 2 49 tells us 49 of offspring homozygous dominant 2pq 42 q 2 09 also same constant over generations will remain in HW equilibrium of phenotype under HW equilibrium in population p q 1 allele frequency in offspring 0 7 p 0 3 q as parent E To maintain equilibrium 1 There has to be no mutation 2 There can t be mating 3 Can t have natural selection 4 Has very large pop size 5 There can t be gene flow IV Genetic Polymorphism 1 ABO Blood Groups B Genetic variation 1 Comes from mutation 2 Recombination a During meiosis 3 Preserved in a population a Diploidy b Balanced polymorphism A Multiple alleles for any given gene that s present in a population i 2 or more alleles are going to persist in a population over generations as a result of natural selection ii Heterozygote advantage ex sickle cell anemia