Quest 4 Flashcards
Actual frequencies mirror expected frequencies when sample sizes are very large.
law of large numbers
process of random fluctuation in allele frequencies due to sampling effects in finite populations (e.g, island populations, limited resources, climate change, humans, etc.)
Genetic Drift
accounts for the effects of various evolutionary forces (genetic drift, mutation, selection, or allele frequencies over time)
Wright-Fisher Model
Estimated from allele frequencies
Expected heterozygosity
estimated from individual genotypes
Observed Heterozygosity
Actively breeding population size
Effective Population Size
Effective population size (variable)
Ne
Heterozygosity (Variable)
He
An event that drastically reduces the size of a population
Population Bottleneck
Species expand into a previously unoccupied area
Leading Edge Expansion
- Most variation in a population is selectively neutral
- Most changes in the DNA are selectively neutral
- Critical process responsible is drift substitution, where a base changes due to a mutation and is subsequently fixed in the population. (Most mutations are not manifest in the phenotype = Synonymous substitution)
Neutral theory of Mol. Evolution
base changes due to a mutation and is fixed in a population (often non deleterious)
Substitution
Change of entire gene or AA code
mutation
nonfunctional segements of DNA that resemble functional genes
pseudogenes
Good mutation at non-syn site that goes to fixation/purges other random mutations
positive selection
weeding out mutations that change AA/lots of mutations at synonymous sites
Purifying selection
Estimate timeframe by number of mutations by branch. Useful when comparing a single locus over a short time for closely related organisms.
molecular clocks
- How gene copies spread through finite populations over time
- Number of generations that we must go back for a population to be reduced to two parental lineages. (usually 2N generations)
o Population size largest factor - UNDERSTANDING RECENCY OF COMMON ANCESTRY
Coalescent time
Multiple genes contribute to a single trait, creating a huge amount of variation. Additive genetic effects.
Polygenic traits
Near continuous variation due to polygenetic traits.
additive genetic effects
Not new variation, but a new assortment of mendelian variation when multiple genes control “one” trait. Usually outside the norm
Ex: Being taller than your mom and dad, not a mutation, rather a new combination of alleles.
Latent Variation
Two or more alleles interact in a non-additive way
Epistasis
Set of alleles, one at each locus on a single chromosome. Or in a gamete.
- ABc or abC or aBc
Haplotype
whole organism
- Aa Bb Cc or AA bb CC …..
Genotype
Two genes located on the same chromosome
Physical Linkage
Frequency of association of their different alleles is higher or lower than what would be expected if the loci were independent and associated randomly
Linkage Disequilibrium
Alleles selected for, not because of its performance, rather the alleles around it are good
Genetic Hitchiking
Loss of surrounding alleles when a deleterious mutation is selected against
Background selection
- Random chance
- Fixation occurs very quickly
- Heterozygosity is lost, very quickly
3 Consequences of Genetic Drift
- Studied using microsatellites
- Short term evolution b/c they are
o Selectively neutral
o Change easily due to strand slippage - As area of the island increased, number of alleles increased
Divergence between populations Lava Lizards
- Northern Elephant seals hunted to almost extinction = bottleneck
- Alleles compared to southern elephant selas that did not get hunted
- Far more alleles for southern vs. that of northern
o Takes forever to rebound and mutate alleles
Northern Elephant Seals
Spruce trees in LEE Low diversity within populations, High between populations
Spruce Trees
- Selection
- Rate of Genetic Recombination
- Mutation Rate
- Genetic Drift
- System of Mating
- Population Structure
- Genetic Linkage
Factors that influence linkage disequilibrium
