Theme 4c Pt 1 Flashcards
What is genetic drift
A process that is independent of phenotype/alleles and is random. Sampling error
Change in alleles frequencies due to chance in finite populations (small populations)
When does genetic drift have the most effect
When the populations are small
Less variance in a small population
If you only have one allele for a gene what does this mean for its heterozygosity
There is not heterozygosity
What does it mean when an allele (A) is fixed
If the allele is fixed over time, it is constant, so the other allele (a) is eliminated.
A/A
What does it mean when an allele (A) is eliminated
The other alleles is fixed (a) and the (A) is gone forever
What happens to elimination and fixation in larger populations
The allele gets neither fixed or eliminated since the population is big. It’s stays relatively the same frequency
What is bottleneck
Temporary reductions in population size that cause drift and reduce variation because only the alleles of the small remaining population is present.
This causes genetic differences between populations.
What causes genetic drift
The founder effect
Bottleneck
What is the founder effect
When New populations are started from a small number of individuals leaving the larger group
Depending on the alleles they take with them some can be fixed and some eliminated
What does genetic drift do to genetic variation in populations?
Reduces genetic variation and causes populations divergence
What is interbreeding
Mating with relatives
What is outbreeding
Mating with non relatives (less closely related)
What is assortative mating
Individuals with similar geno/phenotypes mate with each other (rather than others) more than expected under a random mating pattern
What is non random mating
Choosing to Mate with individuals that are more or less closely related than those from a random mating population
What causes inbreeding and why is it HWE violation
Small populations
Mating system (mating with relatives, cousins)
Choosing to Mate more frequently
Does inbreeding affect allele and genotype frequencies
No just genotype. Allele frequency’s are not changed
What is the consequence of inbreeding, why
Reduced fitness, because rare deleterious alleles are more likely to combine in homozygotes.
They lose heterozygosity and become homozygous recessive
What are the three types of natural selections
Directional
Stabilizing (aka balancing)
Disruptive
What is directional selection
Individuals of a certain extreme phenotype are favoured
Individuals at one end have higher fitness and other end has lower fitness
The trait mean shifts toward one end
What is stabilizing selection
Individuals with intermediate phenotype are favoured (grey moths) and extremes phenotype are selected against (black white moths)
Variance decreases between generations, but the trait mean doesn’t change
Heterozygote advantage
What is an example of the advantage in stabilizing selection
Sickle cell anemia, extreme SS phenotype had more extremes anemia but heterozygote AS have mild condition
AA extreme get ver bad malaria
What is balancing selection
It is like stabilizing selection, selecting against one extreme for a period of time then eventually selecting against the other extreme
Looks like directional selection in short term
What is disruptive selection
Both extreme phenotypes are favoured and the intermediate is selected against
Average individuals have lower fitness, but the trait mean doesn’t change
When does natural selection have the most powerful effect
When the population is large
Small advantages in fitness can lead to large changes over the long term
What happens when there is no selection
The fitness of each phenotype is equal, no selective pressure
So there is no selection
What is viability selection
Ability to survive
What is fecundity selection
Ability to reproduce
What is sexual monomorphism
When you can’t tell if the species are male of female by their genetalia and phenotype
What is sexual dimorphism
When you can tell a difference between a male and female based on genetalia
When is natural selection inevitable
When there is variation in phenotype, fitness differences, and inheritance
What causes fitness differences
Mating ability, fertilizing ability, fertility, and survivorship
What did Darwin do to define selection due to mating and fertilization ability?
Defined it as sexual selection, different than natural selection (heritability)
What is the difference between natural and sexual selection
The outcome may be different but the process is the same
What is intrasexual selection
Fitness differences that result from the ability of same sex individuals to compete for mating opportunities (male-male competition)
What is intersexual selection
Fitness differences that result from choosing specific males and females to mate with.
