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U of M GCD 3022 - Inheritance
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GCD 3022K. Conklin Lecture 40Outline of Last Lecture I. Genetic drifa. Population sizeb. Bottleneck effectII. Hardy-Weinberg Equilibriuma. PTC Exampleb. Tongue Rolling Examplec. Sheep ExampleIII. Inbreeding a. Allele and genotype frequenciesb. Rare recessive genetic diseasesOutline of Current LectureI. Inheritancea. Inbreedingb. Monomorphic vs. Polymorphic c. Hemophilia exampleII. Hardy-Weinberg equilibriuma. 2pqb. Example c. Rabbit exampleIII. Microevolutiona. Genetic drifb. Mutation and mutation ratec. Natural Selectiond. Migratione. Nonrandom matingCurrent LectureI. Inheritancea. Inbreeding: increases the proportion of homozygous individuals in a population.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.b. Monomorphic vs. Polymorphic: monomorphic allele is one that accounts for at least 99% of all alleles for a given gene. A polymorphic allele is one of at least twothat exist for a given gene. c. Hemophilia example: in humans, Hemophilia A is a recessive, X-linked trait and the allele frequency of Hemophilia A is 1 and 10,000 (0.0001). The other allele for this gene is the wild type allele. Males can be affected or unaffected but females can be affected, unaffected carriers, or unaffected homozygous for wild type. i. Allele frequencies of mutant and wild-type alleles in human population: Frequency of mutant allele = 0.0001 = q. 1-q = p. p = 0.9999.ii. Among males, the frequency of affected individuals is: 0.0001 because males only need to inherit one copy of the mutant X chromosome to be affected. This number is equal to the frequency of the allele in the population. II. Hardy-Weinberg equilibrium: most natural populations are not in Hardy-Weinberg equilibrium.a. 2pq: represents the frequency of all heterozygotes.b. Example: a population that is 36% homozygous recessive for a given gene means that:i. The frequency of allele a in the population is: (sq. rt. of 0.36) = 0.6.ii. Frequency of allele A is: 1 – 0.6 = 0.4iii. Frequency of Aa genotype: 2(0.6)(0.4) = 0.48c. Rabbit example: population of 6,340 rabbits and 450 have short toes (recessive trait). Population is assumed to be in Hardy-Weinberg equilibrium.i. Frequency of short toes (tt) = q2 = 450/6340 = 0.071. The square root of this number is q which is 0.266, the frequency of the t allele. ii. Frequency of long toe allele (T) = 1-0.266 = 0.734.iii. Number of rabbits that are heterozygous and carry t allele: 2pq = 0.39 (39% of population). 0.39*6340 = 2472 animals that are heterozygous.III. Microevolutiona. Genetic drif: change in genetic variation from generation to generation due to random sampling error. Has a greater effect on small populations. Can involve thebottleneck or founder effect. A possible outcome of genetic drif is allele fixation.b. Mutation and mutation rate: changes in DNA sequence that result in phenotypic change. Have a very small effect on changing allele frequencies in both large and small populations.c. Natural Selection: the environment selects for individuals that favor survival and reproductive success. This can result in changes in allele frequency of large and small populations. d. Migration: introduction of new alleles into a population by gene flow. This can change allele frequency if the influx of migrants is large compared to the recipient population or if the recipient population is small. e. Nonrandom mating: individuals select mates based on phenotype or genetic lineage. This can change the relative proportion of homozygotes and heterozygotes but does not change the allele frequencies in large or small


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U of M GCD 3022 - Inheritance

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