MICROBIOLOGY EXAM 4

micro bio blah blah

What does a population's gene pool include?

A population's gene pool includes all the alleles present in the population.

Why does a single individual typically have only a small fraction of the alleles present in a population?

Diploid organisms have a maximum of two different alleles at each genetic locus, so a single individual can only possess a small fraction of the population's genetic diversity.

Define population genetics.

Population genetics is the study of genotypes in a population.

What is the difference between genotype, phenotype, and allele frequencies?

Genotype frequency: Proportion of a specific genotype in the population. Phenotype frequency: Proportion of a specific phenotype in the population. Allele frequency: Proportion of a specific allele in the population.

Why is understanding frequencies important for studying the evolution of populations?

Evolution is best understood in terms of changes in genotype, phenotype, and allele frequencies.

Who independently derived the Hardy-Weinberg principle, and in which year?

Godfrey Hardy, an English mathematician, and Wilhelm Weinberg, a German physician, in 1908.

What does the Hardy-Weinberg principle state about allele frequencies in a population?

It states that allele frequencies in a population remain constant unless one or more factors cause them to change.

List the five conditions necessary to maintain genetic equilibrium.

1. No mate choice (random mating). 2. No mutations. 3. No genetic drift (large population size). 4. No gene flow. 5. No natural selection.

Why is the Hardy-Weinberg principle considered an idealized model?

It represents a situation of no evolution, which seldom occurs in natural populations.

What is represented by p + q = 1 in the Hardy-Weinberg equation?

p represents the frequency of the dominant allele, and q represents the frequency of the recessive allele.

How is p^2 + 2pq + q^2 = 1 used to describe genotype frequencies?

p^2: Frequency of homozygous dominant genotype (AA). 2pq: Frequency of heterozygous genotype (Aa). q^2: Frequency of homozygous recessive genotype (aa).

What constitutes microevolution in a population?

Changes in allele, genotype, or phenotype frequencies within a population.

Name the five main causes of microevolution.

1. Nonrandom mating. 2. Mutation. 3. Genetic drift. 4. Gene flow. 5. Natural selection.

How does nonrandom mating influence genotype frequencies?

It changes genotype frequencies by increasing homozygosity, especially through inbreeding or assortative mating.

How do mutations contribute to genetic variation?

Mutations introduce new alleles and increase genetic variability, which natural selection can act upon.

Why are mutations considered a source of deviation from Hardy-Weinberg equilibrium?

They alter allele frequencies by introducing new alleles into the population.

What is genetic drift, and how does it affect small populations?

Genetic drift is the random change in allele frequencies, which can significantly reduce genetic variation in small populations.

Explain the bottleneck effect and provide an example.

The bottleneck effect occurs when a population's size suddenly decreases due to environmental factors, leading to altered allele frequencies. Example: Cheetahs' reduced genetic diversity.

What is the founder effect, and where is it commonly observed?

The founder effect occurs when a small group establishes a new population with different allele frequencies. Example: Amish population in Pennsylvania.

How does gene flow affect genetic variation between populations?

It homogenizes allele frequencies and increases genetic similarity between populations.

Why has gene flow increased in human populations in recent history?

Increased migration and interbreeding among diverse populations.

How does natural selection influence allele frequencies in a population?

It increases the frequency of alleles that improve reproductive success.

Explain how natural selection operates on an organism's phenotype.

It acts on individuals based on their phenotype, but evolutionary changes occur at the population level.

What is the difference between stabilizing, directional, and disruptive selection?

Stabilizing: Favors intermediate phenotypes. Directional: Favors one phenotypic extreme. Disruptive: Favors two or more phenotypic extremes.

Provide examples for each mode of selection.

Stabilizing: Human birth weight. Directional: Beak size in Darwin’s finches. Disruptive: London’s peppered moths.

What are the sources of genetic variation in a population?

Mutation, crossing over, independent assortment, and random fertilization.

What is genetic polymorphism?

The presence of two or more alleles for a given gene locus in a population.

How does balanced polymorphism differ from genetic polymorphism?

Balanced polymorphism is the persistence of two or more alleles due to natural selection.

What is heterozygote advantage, and what is an example of it?

When heterozygotes have higher fitness than homozygotes. Example: Sickle cell anemia provides resistance to malaria.

Explain frequency-dependent selection and provide an example.

Some phenotypes are advantageous when rare. Example: Rare prey phenotypes may avoid predation.