G16-17 Flashcards
what is genetic variation
described in terms of no. of allelss at gene loci and there frequencies
evolution = change in allele freq between generation
what is a population
a group of potentially interbreeding individuals in a given area
what are allozymes/alloenzymes
variant forms of an enzyme coded for by different alleles at the same locus.
- allow heterozygotes to be distinguished from homos
usually assumed to be neutral
how can you calculate allele frequency for N individuals
calculated from the observed no. of each genotype
= 2Xno. AA + no (Aa) / total
what are the assumptions of the HWE
no overlapping generations equal sex ratio no gene flow(migration/emigration) random mating no selection no mutation infinitely large pop (no random genetic drift
what are the sexes in birds and butterlifes
ZZ = males ZW = females
what is the wahlund effect
reduction in heterozygosity due to formation of sub populations
what are the 4 major causes for deviation from HWE and variation between populations
mutation - back mutation rarer
selection - survivorship reproduction differences
random genetic drift - random sampling
migration - gene flow immigration/emigration
what is the mutation rate `
mu u
what is the pā freq if mutation rate is mu
and what does it assume
p - up
assumes back mutation is negligable
what is change in alelle frequency after t generations with mutation rate mu
pt= pe^-ut0
again negligble back mutation
what is the fitness
the contribution of a phenotype/genotype to the next generation
what is absolute fitness
actual no. of viable offspring a pheno/genotype leaves on average
what is the strength of selection/selection coefficient (s)
proportionate reduction in fitness relative to standard
what would be the relative fitness of individuals with AA 8/10 Aa 8/10 and aa 6/10 survival to adulthood
1
1
0.75 so s = 1-0.75 = 0.25 so (1-s)
how do you calculate the mean fittness of a population W
sum of the surviving adult genotypes after selection
so add in the selection to those selected against
what did the experiment on Culex pippiens insecticde resistance show
what is this an example of
- chloryfiros interferes with function of Acetylcholinesterase
Ace^R gives immunity to chloryfiros insecticide
over 22 years in exposed and non exposed showed that Ace^R freq increased
also did control for asparate amino transferase 1 not involved in insecticide resistence showed freq didnt change between pops
directional selection
what is balancing selection
when allele is not advantageous in all situations so more than one allele is maintainted in the population
eg. allele adv in heterozygotes relative to homo or advantageous when rare eg. sickle cell
what is purifying selection
disadvantageous mutations removed as they arrise
what is non random mating the types
dissortative - unlike individuals mate
assortative mating - like individs mate
inbreeding - needs reference pop - more likely to inbreed than chance
what is the expected heterozygosity in random mating
2pq
what does it mean if H0
deficit of heteros and excess homos due to inbreeding
what does it mean if H0=HE
no deficit of heteroz no inbreeding random mamting in HWE F =0
what does it mean if H0>HE
outbreeding inbreeding avoidance.
