population genetics Flashcards
locus
physical position of a gene or marker along a chr.
allele
different form of a gene
genotype - diploid
made up of 2 alleles
homozygote
2 identical alleles
heterozygote
two diff. alleles
polymorphism
gene or phenotype with more than one form
what does population genetics study and why?
freq. of alleles
what determines genetic composition
genetic disease - basis, history, freq.
what do p and q stand for in HWE
each allele in a population
HWE observes that…
independently observed allele freq. can be used to predict next gen.
HWE assumes:
Random mating No natural selection A large population size No migration No mutation
what does HWE show?
how genetic variation is maintained
which gene mutated in peppered moths
cortex gene
M (melanic mutant) dominant to + (peppered WT)
Bernard Kettlewell exp.
mark and recapture peppered moths in rural areas and outside Birmingham
recaptured more better adapted moths as others were eaten
relative fitness equation
reproductive/ survival rate of each genotype
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highest reproductive/ survival rate of one genotype
selection coefficient equ.
highest rel. fitness (1.0) - rel. fitness of other genotype
positive selection
when one allele has an advantage over the other
loss of variation
where is coat colour gene in rock pocket mice
MCR1
dark (D) is dominant - DD Dd
light (d) is recessive - dd
HIV drug resistance, mutation, drug, time, why, how is it overcome
drug - 3TC , takes 4 months
mutation - 184th amino acid, reverse transcriptase Ez resistant
HIV has high mutation rate - 2.5 day gen. time = large population and lots of new mutations
administer 2+ drugs at once
recombination (HIV)
new combinations of alleles produced
RT switches between genomic templates in replication (similar branches on a phylogenetic tree combine)
HIV is resistance to both drugs
recombination (HIV)
new combinations of alleles produced
RT switches between genomic templates in replication (similar branches on a phylogenetic tree combine)
HIV is resistance to both drugs
sickle-cell anaemia mutation and genotype
recessive mutation in B-hb gene
heterozygote selected for and maintained in population as helps with malaria resistance
departs from HWE as more heterozygotes (SA) than expected
balancing selection
heterozygotes are fitter than homozygotes
e.g. sickle cell anaemia
maintains variation
kuru prion disease
mutation at PRNP gene
under balancing selection when Kuru was present
know this because women not exposed are in HWE but women that were aren’t (selection happening) and heterozygote is fittest
genetic drift in small populations
process of losing genetic variation by chance
faster than in bigger
small populations are less polymorphic (fewer phenotypes)
