BIOL 1107 1nd Edition Lecture 33 Outline of Last Lecture I Population Change II Thomas Malthus Carrying Capacity III Passenger Pigeon Indigenous Birds Outline of Current Lecture I II III Gene Pool Allele Frequency Examples Current Lecture I Gene Pool II Gene Pool set of all genes or genetic information in any population usually of a particular species o Proves to be the basic level at which evolution occurs o A large gene pool indicates extensive genetic diversity which is associated with robust populations that can survive bouts of intense selection Low genetic diversity can cause reduced biological fitness and an increased change of extinction although as explained by genetic drift new genetic variants that may cause an increase in the fitness of organisms are more likely to fix in the population if it is rather small Allele Frequency Allele frequency how often that gene is seen in the population Q Dominant alleles occur more frequently in a population than recessive alleles o A False just because gene is dominant doesn t mean it is more frequent Calculating Allele Frequency Q What is the frequency of the M allele 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 Blood type M N MN III Number 285 225 490 A 0 53 MM 285 285 490 1060 2000 0 53 MM because each person has two alleles N 0 47 0 53 0 47 1 00 Examples Flower Color in Pea Plants Q What is the frequency of the P allele Flower color Purple White Number 750 250 1000 White flowers homozygous recessive Hardy Weinberg equation Q a population has a gene with two alleles A and a The frequency of A 60 and of a 40 The frequency of the genotype should be o AA 0 86 0 6 X 0 6 o Aa 0 48 2 X 0 6 X 0 4 o Aa 0 16 0 4 X 0 4 Observed Expected So what An allele for the gene CCR5 is believed to confer resistance to HIV when homozygous Q If the frequency of the CCRD allele is 10 What proportion of the population would you expect to be resistant to HIV A 0 1 X 0 1 0 01 1 resistant to HIV Individuals that are heterozygous for CCR5 may have partial resistance to HIV Q If the 4 of a population is homozygous recessive for CCR5 what would you expect to be heterozygous A 2pq 2 x 0 8 x 0 2 0 32 32 o q 2 0 04 o q 0 2 Hardy Weinberg equilibrium o M p 0 53 o N q 0 47 MM 285 1000 p 2 0 63 x 0 63 28 1 MN 490 1000 2 x 0 63 x 0 47 49 8 Q You observe the following population Genotype AA Aa Aa Number 800 100 100 Total 1000 p 0 85 800 800 100 2000 q 0 15 p 2 0 722 72 2 q 2 0 0225 22 5 2pq 0 265 26 5 Is this population in Hardy Weinberg equilibrium NN 225 1000 0 47 x 0 47 22 09 o 1 Yes 2 No When Hardy Weinberg is not at equilibrium population is evolving
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