Final
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population
-a freely interbreeding group of individuals living together in time and space
gene pool
sum of genetic info present in a population
phenotype
a morphological, physiological, biochemical, or behavioral characteristics of an individual organism
genotype
the underlying make up of phenotypes
locus
a site on a chromosome (or the gene that occupies the site)
gene
allele
an alternate form/ version of a particular gene/ locus
allele (gene) frequency
the relative proportion of a particular allele @ a single locus in a population (b/w 0-1)
genotype frequency
mutually exclusive
-dependent events -both cannot occur (1+6 + 1/6)= 1/3 -1 or 2
how many alleles per locus?
2
Hardy-Weinberg Law
1.) frequency of alleles doesn’t change from generation to generation (frequency doesn’t evolve) 2) offspring genotype frequencies can be predicted from the parent allele frequencies
HW assumption
1) no selection 2) no mutation 3) no gene flow or migration 4) no genetic drift (large population)(exchange of genes) 5) random mating
what does any violation of HW mean?
evolution
Can HW occur in a gene-by-gene basis?
no total genomic HWE is exceptionally rare
implications of HW principle
1) a random mating population w no external forces acting on it will reach the genotype equilibrium 2)any disturbance of the allele frequencies leads to a new equilibrium after random mating 3) amt. of variation is maximized when gene frequencies are intermediate
where can most copies of a rare allele be found?
in heterozygotes
4 primary uses of HW principle
1) compute genotype frequencies from generation to generation, even w selection 2) serves as a null model in tests for natural selection, nonrandom mating, etc, by comparing observed to expected genotype frequencies 3) forensic and disease analysis 4) expected heterozygosity- provides a useful means of summarizing the molecular genetic diversity in natural populations
2 ways to quantify genetic diversity in population
polymorphism- proportion of loci w more than 1 allele in pop heterozygosity- proportion of heterozygotes in a pop. at a SINGLE locus OR proportion of loci heterozygous in an individual genome
what does a true null hypothesis mean?
-we are in HWE -would expect sample of this size to show this much departure (or more) from expectations less than 5% of time
Allozymes
enzymes used as molecular markers to assess different alleles (show high heterozygosity) previously thought that pop wouldnt be variable because 2 allele would grant “best” fitness
what causes genotype frequency differences?
the randomness due to punnet squares
migration (gene flow)
cause allele frequencies of population to change - powerful mechanism for small pop. really quickly -leads to gene flow which tends to homogenize allele frequencies (populations) -> stops process of speciation.
inbreeding
-direct violation of hw because violates random mating due to consanguineous relationships -causes deficit of heterozygote -selfing is most extreme form of inbreeding