Oct23LecNotes - October 23 Lecture Notes Written by Dr...

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October 23 Lecture Notes Written by Dr Balko F (ppt) Routine Class Matters ~ Reading assignments for Today: Chp 13, 14, and 19. Prelim #2 is Tuesday Nov 4 th o Be sure to check out Review Guide that will be posted on BLACKBOARD by next Tues. o Coming Soon ~ Harry will announce special Office Hours for next week. From Last Lecture… (ppt SERIES) BLUE-FOOTED BOOBIES MICROEVEOLUTION EXAMPLES Note: you will have to compute the answer to a population genetics question— similar to what you see in these slides. Hardy-Weinberg equilibrium states that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool [Figure 13.7 B] Which allele is dominant and what does that mean? Why are there 500 animals and 1000 alleles in this example (the reason is that you have 2 alleles/”trait” in diploid organisms)? Do you see where 640 W comes from? Figure 13.7 C ~ We can follow alleles in a population to observe if Hardy- Weinberg equilibrium exists—can you get the numbers in the gold and yellow bars at the bottom of this Figure? Make sure you know how to calculate the numbers in the gold bars at the bottom of Figure 13.7C on this ppt slide. (ppt) Sooooooo…can you estimate allelic, phenotypic, and even genotypic frequencies in a population if we tell you the frequency of one allele? And how could you get that number? If p is the frequency of one allele and q is the frequency of the other, then p + q =1, 1- p = q , and 1- q = p , right? The frequency of one homozygote will be p 2 , of the other will be q 2 , and of the heterozygote will be 2 pq , right? Why? And it all has to add up to 1, as in p 2 +2 pq + q 2 =1—why? So if we tell you that q =0.2, then p =? And so forth... But where did we get the frequency of one of the alleles? 1
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October 23 Lecture Notes Written by Dr Balko (ppt) Example using class data on attached vs un-attached ear lobes About 70% of us have “unattached” earlobes, the result of a dominant allele at that locus… actual data for 2003 were 252 unattached [0.69] and 112 attached [0.31]), so what would be the expected frequencies of each allele and of heterozygotic individuals, IF our population is in Hardy-Weinberg equilibrium for this trait? Let q be the recessive allele, responsible for “attached” earlobes, so q 2 =0.3, q =0.547, and 1- q = p =0.453. The frequency of heterozygotes is 2 pq =0.496 and of homozygous dominants is p 2 =0.205 p 2 +2 pq + q 2 =1, and 0.205+0.496+0.3=1.001 (not bad!!) What else would you need to know to assess Hardy-Weinberg Equilibrium? NOTE: YOU MUST BE ABLE TO CALCULATE ALLELIC FREQUENCIES FOR PRELIM 2. (ppt) Assumptions of Hardy-Weinberg Theorem: KNOW THESE!!! 1. Very large population size [ no genetic drift ] 2. No migration ( no gene flow because the population is isolated ) 3. No net mutations (thus the gene pool is not altered via mutations of alleles) 4. Random mating (no sexual selection) 5. No natural selection (all individuals have equal reproductive success) << The following section of notes is a Population Biology Primer  
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