Question 1

What does the Hardy-Weinberg equation tell us about allele frequencies in a population?

Accepted Answer

The Hardy-Weinberg equation (p² + 2pq + q² = 1) predicts that allele and genotype frequencies remain constant across generations when a population is at equilibrium. Each term represents a genotype frequency: p² for homozygous dominant, q² for homozygous recessive, and 2pq for heterozygous individuals. This serves as a null model to detect whether evolution is occurring.

Question 2

What five conditions must a population meet to maintain Hardy-Weinberg equilibrium?

Accepted Answer

Hardy-Weinberg equilibrium requires random mating, large population size, no mutation, no selection on the gene in question, and no gene flow into or out of the population. Most natural populations violate at least one assumption, making true equilibrium rare. When observed frequencies deviate from predictions, it indicates that evolution or allele frequency change is occurring.

Question 3

How do you calculate allele frequencies from a population's gene pool?

Accepted Answer

Allele frequency is determined by counting the proportion of each allele in the total gene pool. Since each individual carries two alleles, if 40% of alleles are dominant (p = 0.4), then 60% are recessive (q = 0.6). These frequencies must sum to one (p + q = 1), allowing you to predict genotype distributions using the Hardy-Weinberg equation.

Question 4

What is genetic drift and how does it differ from natural selection?

Accepted Answer

Genetic drift is a change in allele frequency due to chance alone, not environmental fitness. Unlike natural selection, which favors adaptive traits, genetic drift represents stochastic evolution occurring randomly in populations. It occurs when breeding pairs are selected randomly, causing some alleles to become more or less frequent by chance rather than because they improve survival or reproduction.

Question 5

What is the founder effect and how does it relate to genetic drift?

Accepted Answer

The founder effect occurs when a small group of individuals establishes a new population in an isolated location, carrying only a subset of the original population's alleles. This new gene pool may have different allele frequencies than the original population purely by chance. The founder effect is a type of genetic drift that shapes future generations based on the random genetics of the founding individuals.

Question 6

How can the Hardy-Weinberg principle be used to detect evolution in a population?

Accepted Answer

By comparing observed genotype frequencies to those predicted by the Hardy-Weinberg equation, scientists can determine if a population is evolving. If measured frequencies differ significantly from predictions, it indicates that one or more equilibrium assumptions have been violated. This deviation reveals that evolution through natural selection, genetic drift, or other mechanisms is occurring.

Question 7

Why does the Hardy-Weinberg equation multiply the heterozygous term by two?

Accepted Answer

The heterozygous term (2pq) is multiplied by two because there are two different ways to produce a heterozygous genotype: an individual can inherit the dominant allele from one parent and the recessive from the other, or vice versa. This accounts for both possible combinations, ensuring the equation accurately represents all genotype frequencies in the population.

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