BIOC51H3 Lecture : Readings 7 notes
11 Aug 2010
School
Department
Course
Professor
Readings 7
Pgs 169-198
-the crucial insight of population genetics is that changes in relative abundance of traits in a
population can be tied to changes in the relative abundance of the alleles that influence them
-a gene pool is the total number of alleles in a population
-a population has evolved when their final allele frequencies are different from their initial
-genetic drift is blind luck that causes a population to evolve unpredictably
-Punnett squares are used in Mendelian genetics to predict the genotypes among the offspring
of a particular male and female
-genotype frequencies among zygotes can also be predicted by multiplying probabilities
-when blind luck plays no role, the allele frequencies are at equilibrium and no evolution occurs
-,Ç[oµo]}v}(ZPvo}}Çzµo~(}PXíóõ]vZ}ÁZ
any allele frequencies can be in equilibrium as long as the sum up to 1
-when there are two alleles at a given locus, their frequencies are p+q = 1 in which A1 is p and
A2 is q
-the probability of a given genotype A1-A1 is p2 = p x p A2-A2 is q2 = q x q and A1-A2 is
2pq
-any allele frequencies can be in equilibrium
-there are two fundamental conclusions of the Hardy-Weinberg equilibrium
-the first conclusion is that allele frequencies in a population will not change throughout
generations
-the second conclusion is that if allele frequencies in a population are given by p and q, the
genotype frequencies will be given by p2, 2pq, and q2
-Hardy-Weinberg equilibrium principle rests on a specific set of assumptions
-the first assumption is that there is no selection and that all members of the population
survive and add equal numbers of gametes to the gene pool
-the second assumption made is that there is no mutation, so no copies of existing alleles were
converted to other existing alleles or new alleles by mutation
-the third assumption made is that there is no migration, so no individuals with certain alleles
move in and out of the population at higher rates than others
-the fourth assumption made is that there are no chance events that cause individuals with
some genotypes to pass more of their alleles to the next generation than others (no genetic
drift)
-the last assumption made is that mating is random }Z]v]À]µo}v[(u}(
the same genotype or a different genotype than others
-the Hardy-Weinberg serves as a null model to contrast events that can cause evolution
-in terms of the CCR5-P32 allele that decreases susceptibility to HIV, if Hardy Weinberg were to
be true, the frequency of the allele would not change
-violation of the first assumption of the Hardy Weinberg equilibrium occurs when individuals
survive to reproduce at higher rates
-selection can lead to evolution when the phenotypes that exhibit differences in reproductive
success are caused by certain genotypes
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