BCOR 12 1st Edition Lecture 4 Outline of Last Lecture I Microevolution mechanisms II Genotypes and allele frequencies III The Hardy Weinberg Principle IV HW assumptions Outline of Current Lecture I The Scientific Process II How to Solve an Expected vs Observed Hardy Weinberg Problem a Used to determine if a population is evolving III Mechanisms that affect Allele Frequencies Current Lecture The Scientific Process I II III IV Develop hypotheses and generate predictions expected data Gather data observed data Compared observed vs expected data Analyze results and draw conclusions Problem Is this human population evolving at a specific gene locus for an neurodegenerative disorder 16 people have the genotype DD 92 people have the genotype Dd 12 people have the genotype dd The D allele is the allele for the neurodegenerative disorder Steps to Solving I II III IV Determine the total number of each alleles Determine allele frequencies p q 1 Determine genotype frequencies Hardy Weinberg equation p2 pq q2 1 Compare expected genotype what you calculated in step 3 to the observed genotype frequencies Number of Individuals Genotype Number of D alleles Number of d alleles 12 DD 24 0 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Total 92 Dd 92 92 12 dd 0 24 124 116 120 Remember that the number of alleles is doubled for there are two alleles in a genotype Example 92 people have genotype Dd so there are 92 D alleles and 92 d alleles in this portion of the population Step 2 p total number of D alleles total number of alleles p 124 240 0 52 q total number of d alleles total number of alleles q 116 240 0 48 Step 3 Determine frequency of each genotype using p2 pq q2 1 p2 0 52 2 0 27 the frequency of the DD genotype pq 2 0 52 0 48 0 50 the frequency of the Dd genotype q2 0 48 2 0 23 the frequency of the dd genotype multiply these frequencies by the total number of individuals in the population to obtain the number of EXPECTED individuals to have these phenotypes 0 27 120 32 0 5 120 60 0 23 120 28 Step 4 Compare expected vs observed observed individuals are the number individuals with the phenotypes given in the problem Genotype Expected Observed DD 32 16 Dd 60 92 dd 28 12 Step 5 What does this data mean Because the observed values are so far from the expected it means that this population is indeed evolving Mechanisms that Alter Allele Frequencies Natural Selection genetic drift including bottleneck and founder effect mutations and gene flow can all alter the allele frequencies in a population Gene flow new individuals are coming into the population and reproduce migration with reproduction Genetic drift random change in allele frequencies in population o is based on what survives and reproduces Bottleneck effect starts with a large population but it then decreases by a large amount significantly shrinking the alleles allele frequencies in the populations o Usually caused by natural disasters i e disease famine etc