Week 22 jalia Flashcards
- Define genetic drift and gene flow and recognize examples of each.
Genetic Drift: A random process that changes allele frequencies in a population due to chance events, often significant in small populations. Example: The bottleneck effect observed in black-footed ferrets, where only a few individuals survive, reducing genetic diversity.
Gene Flow: The movement of alleles between populations through migration of individuals or gametes. Example: The movement of pollen or seeds between plant populations.
- Describe and contrast how genetic drift and gene flow can cause allele frequencies in a population to change over time.
Genetic Drift: Causes random changes in allele frequencies, especially in small populations, often reducing genetic variation and potentially lowering average fitness (e.g., extinction vortex in small populations).
Gene Flow: Introduces new alleles into a population or homogenizes genetic variation between populations, potentially increasing genetic diversity and fitness in some cases or inhibiting local adaptation in others.
- Describe the effect that genetic drift and gene flow have on average fitness and genetic variation in a population.
Genetic Drift:
Effect on Fitness: Often random but can decrease average fitness due to loss of beneficial alleles.
Effect on Genetic Variation: Decreases genetic variation within populations.
Gene Flow:
Effect on Fitness: Can increase fitness by introducing beneficial alleles or decrease fitness by introducing maladaptive alleles.
Effect on Genetic Variation: Increases genetic variation within populations but reduces differences between populations.
- Explain how the presence or absence of gene flow into a population can influence how genetically similar it is to other populations.
Presence of Gene Flow: Makes populations more genetically similar by mixing alleles.
Absence of Gene Flow: Allows populations to diverge genetically due to independent evolutionary processes like mutation, selection, or drift.
- Predict whether gene flow into a population will help or inhibit the population’s capacity to adapt to local conditions.
Help: Gene flow can introduce new genetic material that provides raw variation for selection to act upon, aiding adaptation, especially after bottleneck events.
Inhibit: If gene flow introduces maladaptive alleles or prevents local adaptation by homogenizing differences, it may hinder the population’s ability to adapt.
Gene flow is most likely to:
A. Increase genetic diversity in recipient
population
B. Decrease genetic diversity in recipient
population
A, INCREASE
Define populations in terms of their allele frequencies vs. their genotype frequencies.
A population consists of individuals of the same species living in the same area, where allele frequency refers to the proportion of specific alleles in the gene pool, while genotype frequency refers to the proportion of specific genotypes in the population.
Link Mendel’s principles of independent segregation to the expected ratios of alleles and genotypes in a population.
Mendel’s principles state that alleles segregate independently during gamete formation, leading to predictable genotype ratios (e.g., Aa x Aa producing ¼ AA, ½ Aa, ¼ aa).
Compare the assumptions of Hardy-Weinberg Equilibrium with evolutionary pressures in real life.
Hardy-Weinberg assumes no evolution (no selection, drift, migration, mutation, or non-random mating). However, real populations often experience these forces, causing allele frequencies to change.
Compare expected and observed frequencies of alleles in populations under natural selection using the Hardy-Weinberg Equation.
Expected frequencies are calculated using Hardy-Weinberg, and observed frequencies are obtained from actual data. Deviations indicate evolutionary change, such as selection against a recessive trait.
Summarize at least one example of a genetic disease caused by recessive vs. dominant alleles.
Recessive: Sickle-cell anemia – only appears in homozygous recessive individuals.
Dominant: Huntington’s disease – affects heterozygotes, but persists because symptoms appear after reproductive age.
What if the a allele is deleterious (reduces fitness)? Over several generations, the a allele would:
A. Increase relative to the expected ratios
B. Decrease relative to the expected ratios
C. Stay the same as the expected ratios
Answer: B. Decrease relative to the expected ratios.
What is a fixed allele
when all individuals in a population are homozygous for one allele no other alles for that locus exists in the population
Gene pool
all the alleles of all the genes in all individuals of a population
when is the population at equilibrum
If a population’s expected frequencies match its observed frequencies, and this does not change, then the population is at equilibrium.
