Lecture 6 Flashcards
(25 cards)
What is population genetics?
Population genetics studies the frequencies of alleles in populations and the mechanisms that change these frequencies over time.
Mnemonic: Picture a pie chart showing different colored slices labeled “A,” “B,” “C” to represent allele frequencies in a population.
What is the Hardy-Weinberg Law?
The Hardy-Weinberg Law states that allele frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.
Mnemonic: Visualize a balanced scale with “p” on one side and “q” on the other, symbolizing equilibrium.
What is a population in the context of genetics?
A population is a group of organisms of the same species that can interbreed and produce fertile offspring, capable of gene flow.
Mnemonic: Picture a group of animals crossing a bridge labeled “Gene Flow.”
How is allele frequency represented?
Allele frequency is typically represented as a percentage or decimal fraction (e.g., 0.8 for 80%).
Mnemonic: Imagine a pie with 80% filled in red for “A” and 20% filled in blue for “a.”
How do you calculate allele frequencies for a given population?
Count the total alleles and determine the frequencies using p+q =1
Mnemonic: Think of a box of 100 marbles, where 80 are red (p) and 20 are blue (q), with a label showing “Total = 1.”
What is genetic drift?
Genetic drift is the random fluctuation in allele frequencies due to chance, especially in small populations.
Mnemonic: Imagine a dice being rolled, where each side represents a different allele, emphasizing randomness.
What is the bottleneck effect?
A sharp reduction in population size due to environmental factors, leading to a loss of genetic diversity.
Mnemonic: Visualize a bottle with many marbles being poured through a narrow neck, leaving only a few behind.
What is the founder effect?
Loss of genetic variation when a new population is established by a small number of individuals from a larger population.
Mnemonic: Picture a tiny island with a few animals arriving by boat, carrying only a few traits from the mainland.
What is gene flow?
Gene flow is the transfer of genetic material between populations through migration.
Mnemonic: Imagine arrows moving between two circles labeled “Population A” and “Population B,” symbolizing migration.
What is assortative mating?
A form of non-random mating where individuals with similar phenotypes are more likely to mate.
Mnemonic: Think of pairs of puzzle pieces that only fit with pieces of the same color.
How does natural selection affect allele frequencies?
Natural selection changes allele frequencies by favoring traits that increase survival and reproduction.
Mnemonic: Picture a tree with birds of two colors, where predators only eat the brighter ones, leaving the others to thrive.
What are the assumptions of the Hardy-Weinberg principle?
Random mating, large population size, no selection pressures, no migration, and no mutations.
Mnemonic: Imagine a perfect bubble around a population labeled “No Evolution Allowed.”
What happens if the Hardy-Weinberg assumptions are violated?
Violations cause allele frequencies to change due to factors like genetic drift, selection, or migration.
Mnemonic: Visualize cracks forming in a perfectly smooth glass sphere labeled “HW Equilibrium.”
What is the Hardy-Weinberg equation?
P² + 2pq + q² =1 where p² is the frequency of homozygous dominant 2pq is heterozygous and q² is homozygous recessive.
Mnemonic: Picture a triangle with three sections: “p²” at the top, “2pq” in the middle, and “q²” at the bottom, forming a pyramid of equilibrium.
How do you calculate allele frequency using the Hardy-Weinberg principle?
Start with q² recessive genotype frequency, take its square root for q then calculate p using p + q =1 Mnemonic: Visualize a ladder where you start with q ² at the bottom move up to q and finally reach p at the top
What is the effect of inbreeding on allele frequencies?
Inbreeding increases homozygosity, leading to a higher expression of recessive genetic disorders.
Mnemonic: Picture a family tree with many overlapping branches, symbolizing repeated genetic connections.
What is genetic variation’s role in evolution?
Genetic variation is essential for evolution, as it provides the raw material for selection to act upon.
Mnemonic: Think of a toolbox with diverse tools labeled “Alleles,” ready for natural selection to use.
What is the significance of the example of albinism in Hopi Native Americans?
Albinism frequency is unusually high (1/200) in Hopi Native Americans due to cultural selection and isolation.
Mnemonic: Picture a spotlight on an albino individual in a small Hopi community.
What is the bottleneck effect in northern elephant seals?
In the 1890s, the northern elephant seal population was reduced to 20 individuals, leading to low genetic diversity despite population recovery.
Mnemonic: Imagine a nearly empty bottle with a single seal climbing out, symbolizing reduced genetic diversity.
What is the founder effect in Tristan da Cunha?
Retinitis pigmentosa became common on Tristan da Cunha because a single colonist carried the gene, highlighting the founder effect.
Mnemonic: Picture a small group on an island, with one person holding a glowing “RP” gene.
How does gene flow prevent populations from diverging?
Gene flow allows the exchange of alleles between populations, maintaining genetic similarity. Without it, populations may diverge into separate species.
Mnemonic: Visualize a bridge connecting two islands labeled “Population A” and “Population B,” with arrows moving between them.
What factors cause Hardy-Weinberg equilibrium to break down?
Factors include:
Small populations (genetic drift)
Mutation
Non-random mating
Migration (gene flow)
Natural selection
Mnemonic: Imagine a cracked bubble with labels for each factor, breaking the equilibrium.
What is assortative mating, and give an example?
Assortative mating occurs when individuals prefer mates with similar phenotypes.
Example: Large Bufo toads prefer large mates, and small toads prefer small mates.
Mnemonic: Picture toads of different sizes pairing up based on matching sizes.
How do mutational changes affect allele frequencies?
Mutations introduce new alleles, providing the raw material for evolution and potentially becoming fixed in a population.
Mnemonic: Imagine a glowing “mutation” spark creating a new branch on a genetic tree.
