lecture 10 Flashcards
what is epistasis
2 genes can have epistatic relationship = interact to determine phenotype
describe population genetics
moving from a few organisms to whole populations = new genetic properties and forces emerge
bc enormous genotype an d they change over time
describe emergent population level properties and processes - 3
genotype and allele frequencies
Change in genotype and allele frequencies - over time= evolution
population to population variation - variations between populations in genotype and allele frequencies
describe emergent population genetic level forces
things cause evolutionary change = change allele and genotype frequencies
change in population level variation due to many factors
what can a change in population level variation be due to - 4
mutation
migration
selection
chance = genetic drift
describe frequency of the b blood type across a geographical region - from mendelian genetics to population genes - ex of phenomena
frequency low in spain and portugal and as move to central europe frequency increases
describe frequency of the adh(F) allele over time - from mendelian genetics to population genes - ex of phenomena
one allele of gene = becomes fast allele when flies raised on increased amounts of ethanol = could be due to detoxification of ethanol
nothing happened to the control
describe single gene - allele frequency of sickle cell anemia - from mendelian genetics to population genes - ex of phenomena
sickle cell anemia = when a person has 2 copies of the HbS allele
interferes with circulation and physiology
when one copy = heterozygous = advantage against malaria
describe population level variation - ex setup
dna sequences in sample, n=7 individuals of a population
variation in single nucleotide polymorphisms (SNPs), indels, microstallites
what are microstallites
repeats of agag
describe population level variation - ex results
results = 1-3 have more than 4-7
sequence data = small fraction of genome
can see variations
some segregation of allales or nts, indels = missing part of sequence
what is haplotype variationn
bp 1-35 on chrom 22
not all individuals have same for this chrom = haplotype
what can haplotype variation tell us about + ex
history of population
migration looks to be stepwise for post glacial recolonization
diff parts = have diff amounts of mutations
see history of migration
what do genetics at the population level concentrates on
concentrates on collections of individuals and their genetic properties
especially frequencies of alleles, genotypes, haplotypes in time and space (geography, habitats), snps = single nt polymorphisms
what do genetics at the population level study
studies origin, maintenance and change of allelic and genotypic variation in populations
what does genetics at the population level makes use of
makes use of models to study processes that influence population genetic composition and make predictions about how it will change - in response to selection, migration
theory heavy
abstract way to think about it - predictions
describe gene pool model
populations do not actually have hard boundaries
describe characterizing the gene pool
count alleles of each type
genotype frequencies = AA, Aa, aa (number of each/total people)
alelle frequencies = A and a (alleles/total alleles)
notation for genotype frequencies
for a gene with 2 alleles, A and a
frequency genotypes = fAA, fAa or faa
the sum of fAA + fAa + faa = 1.00
notation for genotype frequencies
for gene with 2 alleles - biallelic loci
frequency of allele 1 - A = p
frequency of allele 2 - a = q
since p+q = 1 then q=p-1 since must sum to one
describe population genetic variance - blood groups locus 2 major alleles, MN
codominance = heterozygous both show up
2 alleles = antigens on blood cells
use reactions since alleles wont work
how to go from genotype to allele frequency
p=fMM + 1/2 fMN
q = fNN +1/2 fMN
Can we calculate genotype frequencies in the next generation if we only know the allele frequencies in the current generation?
yes and no
but yes = must conform to some conditions
HARDY WEINBERG
when can we calculate genotype frequencies in the next generation if we only know the allele frequencies in the current generation
if there is random mating (with respect to this locust), no mutation, no selection, no migration (isolated enough) and no drift
assume very large population and no small population effects
rate of mutant slow - since unlikely to mutate nts
what are frequencies if hardy weinberg
freq AA = p^2
freq Aa = 2pq
freq aa = q^2
describe hard weinberg proportions
When there is random mating, no mutation, no selection, no migration and no drift, the genotype frequencies in the next generation are frequencies OF simple punnet square with 2 hetero
will hardy weingberg last
the frequencies will remain unchanged provided there is continued random mating and absence of evolutionary forces
only need single gen of hardy weinberg then will continue to hold as conditions hold
what is dna fingerprinting
application of hardy weinberg
friend of the innocent
genotyping suspects at many loci (not single, tend to be snps or microsatellite alleles) each assumed to show genotype frequencies predicted by hardyweinberg theory
general formula - hardy weinberg
p^2 + 2pq + q^2 = 1
