Module 13-15 Alteration of Genetic Equilibrium Flashcards
These are processes that cause a change in gene frequency magnitude and degree.
Systematic processes (Ex. Mutation, selection and migration)
These are processes that change the magnitude but not the direction
Dispersive Processes (Genetic Drift and nonpanmictic/nonrandom mating)
This is the ultimate source of genetic variation inclusive of all genetic changes.
Mutation
T/F Mutation occurs at a generally very low rate per generation.
T, 10^-5 or 10^-6 per generation in most loci of most organisms
Two types of mutation and differentiate
Non-recurrent: Rare, small chance of survival
Recurrent: Consequence of altering gene frequencies
If p0 is the initial frequency of gene A and it mutates continuously to a at a rate, and the reverse mutation does not occur, A after n generations becomes pn. How is pn calculated?
pn=po*(1-u)^n
where:
pn = freq of A after n generations
po = initial freq of A
u = rate of mutation
n = number of generations
Given initial A and a frequencies p and q, how will you calculate new frequencies with forward and backward mutations after 1 generation?
freq (A) = p1 = p + (vq) - (up)
freq (a) = q1 = q + (up) - (vq)
where:
u is the forwards rate
v is the reverse rate
How do you calculate for p and q at mutational equilibrium?
At mutational equilibrium, up=vq therefore
p = v/(u+v) and q = u/(u+v)
Using mutational equilibrium, how do you calculate the value of q after any specified generation time with both forward and backward mutation?
(u+v)n=ln((q-qe)/(qn-qe))
where:
q = initial q value
qe = q freq at mutational equilibrium
qn = q after n generations
Algebra go brrrr
Refers to fluctuations in allele frequency that occur by chance, particularly in small populations, as a result of random sampling among gametes.
Random Genetic Drift
Two Causes of Random Genetic Drift
Mendelian Segregation
Finite population size
How to calculate variance in allelic frequency among populations under random genetic drift? What about sampling error?
(sp)^2 = (pq)/2N
where:
N = total population size
p and q = allelic freqs of p and q
(sp)^2 = Variance
To get sampling error/standard dev, get square root of Variance.
The number of breeding individuals in an idealized population that would show the same amount of dispersion of allele frequencies under random genetic drift or the same amount of inbreeding as the population under consideration
Effective Population Size
Causes of genetic drift (3)
Population size reduction by environmental factors
Founder Effect
Genetic Bottleneck
Occurs when a population is established by a small number of individuals resulting in significantly less genetic diversity
Founder Effect
Occurs when a population undergoes a drastic reduction in population size. Emphasis on drastic
Genetic Bottleneck
Four Main Aspects of Random Genetic Drift
▪direction is unpredictable
▪magnitude depends on population size
▪long-term effect is to reduce genetic variation within a population
▪causes populations to diverge
Composite of the forces that limit the reproductive success of a genotype
Selection
Comparative ability of a genotype to withstand selection
Fitness
The extent to which a genotype contributes to the offspring of the next generation relative to the other genotypes in a given environment
Adaptive Value (W)
Also known as fitness or Selective Value
This is the percentage reduction in fitness.
Selection Coefficient (s)
What is the relationship between Adaptive Value (W) and selection coefficient (s)?
W=1-s or s=1-W