Bio115 - Lecture 35
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Bio115 - Lecture 35
Bio115 Lecture 35
Genomic screening for newborns
Screening for large number of genetic diseases
Better/earlier preventative treatement
Genomic screening for personalized medicine
Able to predict responses to different treatments and fine-tune drug therapy for individual
Genetic testing of both patients and pathogens will allow faster and more precise diagnosis of many diseases
What is population genetics?
The study of the genetic makeup of groups of individuals and how a group’s genetic composition changes with time
What are Mendelian populations?
Groups of interbreeding sexually reproducing individuals that share the same gene pool.
What is a gene pool?
A common set of genes in a population
Population geneticists study:
The variation in alleles within and between groups
The evolutionary forces that shape patterns of genetic variation
What causes phenotypic varation within a population?
Genotypic frequency: f(AA)
f(AA) = (number of AA individuals)/N, where N is the number of individuals in the sample
Calculating the frequency of an allele
freq of an allele = (# of copies of allele)/(# of copies of alleles at the locus)
Allele frequency: p = f(A)
f(A) = (2nAA + nAa)/(2N)
Calculate allelic frequencies from individual frequencies
p = f(A) = f(AA) + (1/2)f(Aa)
Calculate allelic frequencies at loci with three alleles
p = f(A1) = (2nA1A1 + nA1A2 + nA1A3)/2N
Calculate allelic frequencies from individual frequencies with three alleles
p = f(A1A1) + (1/2)f(A1A2) + (1/2)f(A1A3)
Calculate allelic frequencies at X-linked loci
p = f(XA) = (2nXAXA + nXAXa + nXAY)/(2nfemales + nmales)
Calculate allelic freq's at X-linked loci from individual frequencies
p = f(XA) = f(XAXA) + (1/2)f(XAXa) + f(XAY)
Study example on slide 15
human MN blood-type antigens
What assumptions does the Hardy-Weinberg law make?
The population is large, randomly mating, and not affected by mutation, migration, or natural selection
The Hardy-Weinberg Law predictions:
: The allelic frequencies of a population do not change
: The genotypic frequencies stabilize (do not change) after one generation in the following proportions:
p^2, 2pq, q^2
The allelic frequencies determine the frequencies of genotypes
If a population meets the Hardy-Weinberg assumptions, can it evolve?
Yes, but it requires external pressure.
When a population is in Hardy-Weinberg equilibrium, the genotypic frequencies are determined by ...
the allelic frequencies