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Lecture 3

BIOL 102 Lecture 3: BIOL102 Boag Lecture #3 Population Genetics and Causes of Microevolution


Department
Biology
Course Code
BIOL 102
Professor
Wayne Snedden
Lecture
3

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-utatio does’t eall chage allele feuec to a sigificat etet
Hardy Weinberg
-expectation of allele frequency from one generation to the next
Iclicker: For H W equilibrium to obtain, which of the following conditions must not be true
A. populations are very large
B. Individuals mate at random
C. Genotypes vary in fitness selection! That natural selection is favoring one genotype at the expense
of other genotypes. H-W assumes equal genotypes
D. Immigration and emigration are zero
E. Mutation is rare or absent
-all the other assumption are necessary for HW equilibrium to occur
-knowing p and q can use binomial expansion to find genotype frequencies
-at any given locus has two different alleles modeling sexual reproduction (two homologous
chromosomes at the homologous loci
-two same homozygous (product of individual probabilities p2 or q2, two different heterozygous (2pq)
-42% heterozygotes will produce alleles that are 70% A and 30% a
-pool of sperm and eggs with 70% A, 30%a
-sexual reproduction and nature ialter phenotypes and genotype frequencies
First violation of H-W equilibrium: nonrandom mating
-inbreeding: mating between relatives
-inbreeding depression: offspring produced by mating between close relatives have lower
fitness!
-balancing selection: heterozygotes have higher fitness
-self fertilize
-positive mating
-all cause decrease heterozygotes and increase homozygotes
-able to self pollinate, but if there are no plants, can fertilize their own seeds, and those seeds will have
reduced fitness like a backup mechanism
-outcross
-extreme inbreeding: sudden onset of self fertilization
-one locus two alleles, equal frequencies, 1:2:1, after one self fertilize,
-homozogytes can only produce homozygote offspring with self fertilization
-heteroxygotes can produce A1A1, A1A2 and A2A2. The heterozygote decrease by a half and the
homozygotes fit into the other homozygotes
-will not change allele frequencies, but genotype frequencies differences!
-if homozygote recessive is less fit, inbreeding more homozygotes may cause a weaker population
-inbreeding depression can cause difference in allele frequencies, now available for natural
selection
-reversion back to hw equilibrium only takes one generation of random mating sexual reproduction
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find more resources at oneclass.com
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