Genetics Flashcards
What are the microevolutionary forces that can alter allele frequencies?
- Mutations
- Gene flow
- Genetic drift
- Natural selection
- Assortative mating
These forces contribute to changes in genetic variation within populations.
Define mutation in the context of genetics.
Change in the sequence of bases of DNA along a chromosome
Mutation is the ultimate source of variation as it creates new alleles.
What is the ultimate source of variation in populations?
Mutation
New alleles are created through mutations, although their rates are low.
What happens to a new allele once it enters a population?
- It may stay in the population
- It may get fixed over generations
Fixation refers to a scenario where eventually all alleles in the population are of one type.
What is genetic drift?
Change in allele frequencies due to chance (random events)
Genetic drift can lead to a loss of genetic diversity, particularly in small populations.
How does genetic drift affect small populations?
- Loss of genetic diversity
- Harmful alleles may become more common
Genetic drift has more pronounced effects in smaller populations due to their limited genetic variability.
What is a bottleneck in genetic drift?
An extreme reduction in population size leading to loss of genetic diversity
This can result from catastrophic events like natural disasters.
What is the founder effect in genetic drift?
Occurs when a few individuals disperse and start a new population with limited genetic diversity
This can lead to a population that is less adaptable and more vulnerable to diseases.
What role does natural selection play in evolution?
Acts on the phenotype, not the genotype, based on variation in net reproductive success
Natural selection filters genetic variation based on survival and reproduction.
What are the types of natural selection?
- Stabilizing
- Directional
- Disruptive
Each type favors different traits within a population.
What is heterozygous advantage?
When heterozygotes have higher relative fitness than homozygous genotypes
This can maintain multiple alleles at a locus even if one is harmful.
What is sexual selection?
Occurs when certain traits increase mating success
It is influenced by the higher reproductive costs for females.
What is assortative mating?
Individuals with similar phenotypes mate with one another more frequently than expected
This leads to less genetic variability and increased extinction risk.
What does the Hardy-Weinberg principle predict?
The constancy of allele frequency from generation to generation in the absence of evolutionary forces
It assumes conditions like no migration, no mutation, and random mating.
List the assumptions of the Hardy-Weinberg principle.
- Diploid genotypes
- Sexual reproduction
- Non-overlapping generations
- Males = females
- No migration (gene flow)
- No mutation
- No selection
- Large population (no genetic drift)
- Random mating
These assumptions create a baseline for studying evolution.
