Lecture 6 Flashcards
Genetic Drift
What is genetic drift
Changes allelic frequency due to random chance
Random events unrelated to fitness
Favors either loss or fixation of an allele
Faster in smaller populations
What is the bottleneck phenomenia
The population reduces dramatically and then rebuilds - this may be due to an natural disaster
Randomly eliminates members without regard to genotype
Surviving members may have allele frequenceis different from original population
Allele frequencies can drift substantially when population is small
New population likely to have less genetic variation
What is the founder effect
Small groups of individuals separates from a larger population and establishes a new colony
Relatively small founding population expected to have less genetic variation than original population
Allele frequencies in founding population may differ markedly from original population
What is neutral variation
Much of the variation seen in the natural populations is caused by genetic drift
Does not preferentially select for any particular allele
Most genetic variation is due to the accumulation of neutral mutations that have attained high frequencies due to genetic drift
Neutral mutations do not affect phenotype so they are not acted upon by natural selection
What is the main idea behind the neutral theory of evolution
The main idea is that much of the modern variation in gene sequences is explained by neutral variation rather than adaptive variation
Sequencing data supports this idea
When does gene flow occur
It occurs when individuals migrate between populations having different allele frequencies
Migration tends to reduce differences in allele frequencies between the two populations
Tends to enhance genetic diversity within a population
What is nonrandom mating
One of the conditions required to establish the Hardy-Weinberg equilibrium is random mating
Individuals choose their mates irrespective of their genotypes and phenotypes
What is assortative mating
Individuals with similar phenotypes are more likely to mate
Increases the proportion of homozygotes
What is disassortative mating
Dissimilar phenotypes mate preferentially
Favors heterozygosity
What is inbreeding
The choice of mate based on genetic history
Does not favor any particular allele but does increase the liklihood the individual will be homozygous
May have negative consequences with regard to recessive alleles
Lower mean fitness of a population if homozygous offspring have a lower fitness value
What is inbreeding depression
Decreases the population has more bad traits
Can attempt to introduce new population to increase genetic diversity
