Ch08P2 Flashcards
Why is it that populations
do not become homozygous (or nearly so)?
alleles favored by selection may not become fixed in a population
The probability of fixation depends on what?
the initial allele frequency
When a new mutation rises, does it start at low or high frequency?
low
Relating to genetic drift, would a new mutation goes to fixation faster in small or large population size?
small population size
What happens when population size is smaller than actual size?
bottlenecks & sex ratio biases reduce chance of fixation of beneficial mutation
*population size matters
Explain Kimura’s rule of thumb
selection dominates when s > 1/2Ne drift dominates otherwise
The interplay between drift & selection depends on what?
the strength of selection & population size
What happens when selection is strong?
a rare allele can go to fixation even if population is small
What happens when selection is weak & population is small?
probability of fixation is small, & drift can eliminate advantageous allele from population
What determine allele frequency change over generations?
drift & selection acting together
define substitutions
A new allele made by mutation becomes fixed in population (replaces previous allele)
The Neutral Theory proposes what?
1) Most variation present in a population is selectively neutral
2) Most changes in DNA or amino acid sequence over time are selectively neutral, including differences between species
What is the critical process in evolution?
GENETIC DRIFT
What portions of a protein will be conserved, & what portions will be variable?
Most important portions of a protein will be
more conserved, less important will be more variable
Researchers suggested that most mutations are what?
effectively neutral
