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Recombination, Mutation, Genetic Drift, Gene Flow Also evolution Recombination Remember This is when recombination occurs Shuffling of chromosomes/genes/alleles Also crossing over Remember Meiosis? fertilization? Coming together of shuffled genes New alleles not created, just rearranged for more genetic variability 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 If it causes severe reductions, usually ends with death Neutral mutation changes base sequence but has no effect on survival or reproduction mutation ex. – corn plant has a mutation that makes it grow faster or larger giving it best access to sunlight and nutrients Beneficial Neutral mutation might prove helpful if the environment changes Genetic Drift Random changes in allele frequencies over time is greatest in small populations – leads to loss of genetic diversity Effect Allele will become more or less prevalent in small pops Bottleneck and Founder Effect Bottleneck Drastic reduction in population size because of severe pressure Founder Effect A few individuals establish a new population Unpredictable genetic shifts occur 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 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 Hardy-Weinberg Principle 1. 2. 3. 4. 5. Random mating Large population No movement No mutations No natural selection Allele frequency in a population will remain constant 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 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?