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Lecture 18

GN 301 Lecture Notes - Lecture 18: Restriction Fragment Length Polymorphism, Mitochondrion, Genetic Drift

Course Code
GN 301
Marian- Elizabeth B.Gardner

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4.2 Population Genetics
Tuesday, November 21, 2017
3:09 PM
Population Genetics
o Study of inherited variation within and beyond populations over time
Gene frequency: allele freq
Population: local group of species among which mating can occur
Evolution: change in genetic composition of population
New species, divergence in two species, extinction
Calculating Genotypes
o F(genotype)= # (genotype) individuals/total # individuals
Calculating Allele Frequencies
o F(S)= [ f(SS) + 0.5 f(SG)]/ total # ind
o F(G)= [ f(GG) + 0.5 f(SG)]/ total # ind
Hardy-Weinberg Law
o If…
Large population
Random mating
No natural selection
No migration in or out
No mutations
o Then…
Allele and genotype frequencies will reach and stay at equilibrium after one
generation of random mating
o P^2 + 2PQ + Q^2
P= freq of dom allele
Q= freq of recessive allele
P^2= freq of hom dom genotype
Q^2= freq of hom recessive genotype
2PQ= freq of heterozygous genotype (carriers)
Use last three as formula to find actual number of individuals with that
genotype by simply multiplying total population by formula (ex: n* 2PQ)
o Most people carry 10 alleles for debilitating disorders
o Maple Syrup Urine Disease
Pee smells sweet
Mental retardation, handicapped, difficulty eating
Autosomal recessive
o Sickle Cell and Malaria
Malaria is prevented in people who have HbS allele because parasite cannot live
there. Unfortunately, the HbS allele is the cause of sickle-cell anemia
find more resources at
find more resources at
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