Recombination, Mutation, Genetic Drift, Gene Flow

1. Recombination, Mutation, Genetic Drift, Gene Flow Also evolution 

2. Recombination • Remember Meiosis? • This is when recombination occurs • Shuffling of chromosomes/genes/alleles • Also crossing over • Remember fertilization? • Coming together of shuffled genes • New alleles not created, just rearranged for more genetic variability

3. Mutations Creates new alleles Beneficial, neutral, or lethal Passed on to new generations if they arise in gametes Can reduce chances of survival and reproduction

4. If it causes severe reductions, usually ends with death Neutral mutation changes base sequence but has no effect on survival or reproduction Beneficial mutation ex. – corn plant has a mutation that makes it grow faster or larger giving it best access to sunlight and nutrients Neutral mutation might prove helpful if the environment changes

5. Genetic Drift • Random changes in allele frequencies over time • Effect is greatest in small populations – leads to loss of genetic diversity • Allele will become more or less prevalent in small pops • Bottleneck • and Founder Effect

6. Bottleneck Drastic reduction in population size because of severe pressure

7. Founder Effect A few individuals establish a new population Unpredictable genetic shifts occur

8. Gene Flow Physical movement of alleles into and out of a population Opposes the effects of mutation, natural selection, and genetic drift Keeps populations similar to one another Increases genetic variability in that new population

9. Cladograms Aka. Phylogenetic tree, branching tree, evolutionary tree Lines not still apparent at present are extinct Do not have to all face the same way

13. Hardy-Weinberg Principle • Random mating • Large population • No movement • No mutations • No natural selection • Allele frequency in a population will remain constant

14. H-W Principle • p2 + 2pq + q2 = 1 • p + q = 1 p2= frequency of homozygous dominant 2pq = frequency of heterozygous q2 = frequency of homozygous recessive p = dominant allele q = recessive allele

15. H-W Principle 1 in 1700 US Caucasian newborns have cystic fibrosis. C for normal is dominant over c for cystic fibrosis. • What percent of the above population have cystic fibrosis (cc or q2)? • What percent of the population do not have cystic fibrosis and are homozygous dominant (CC or p2)? • What percent of the population is heterozygous?