ap bio chapter 21: Concept 21.2: The Hardy-Weinberg equation can be used to test whether a population is evolving

What is a population in genetics?

A localized group of individuals capable of interbreeding and producing fertile offspring.

Why is a liger not considered a part of a population?

A liger is not fertile and cannot produce offspring with another liger.

Why is a mule not part of a population?

A mule is sterile and cannot reproduce.

What is a gene pool?

The total collection of alleles for all loci in a population.

What does it mean if an allele is "fixed" in a population?

Every individual in the population is homozygous for the same allele.

How do you calculate the total number of alleles at a locus in a diploid organism?

Multiply the total number of individuals by 2.

How do you determine the number of dominant alleles in a population?

(2 × homozygous dominant individuals) + (1 × heterozygous individuals).

How do you determine the number of recessive alleles in a population?

(2 × homozygous recessive individuals) + (1 × heterozygous individuals).

What equation represents the total allele frequency in a population?

p + q = 1

What does "p" represent in the Hardy-Weinberg equation?

The frequency of the dominant allele.

What does "q" represent in the Hardy-Weinberg equation?

The frequency of the recessive allele.

What is incomplete dominance?

When a heterozygous individual has a blend of both traits, e.g., red + white = pink.

If 320 red flowers (CRCR), 160 pink flowers (CRCW), and 20 white flowers (CWCW) exist, how do you calculate CR allele frequency?

(320 × 2) + 160 = 800

How do you calculate CW allele frequency in the same population?

(20 × 2) + 160 = 200

How do you find the allele frequency of CR in this example?

p = 800 / (800 + 200) = 0.8 (80%)

How do you find the allele frequency of CW?

q = 1 - 0.8 = 0.2 (20%)

What does the Hardy-Weinberg principle describe?

A population that is NOT evolving.

What happens if a population does not meet the criteria of Hardy-Weinberg equilibrium?

The population is evolving.

What is the Hardy-Weinberg equilibrium equation for genotype frequencies?

p² + 2pq + q² = 1

What does p² represent?

The frequency of the homozygous dominant genotype.

What does q² represent?

The frequency of the homozygous recessive genotype.

What does 2pq represent?

The frequency of the heterozygous genotype.

What are the five conditions required for Hardy-Weinberg equilibrium?

• No mutations

• Random mating

• No natural selection

• Extremely large population size

• No gene flow

Why must there be no mutations for Hardy-Weinberg equilibrium?

Mutations introduce new alleles, changing allele frequencies.

Why must mating be random?

If individuals choose mates based on traits, allele frequencies change.

Why must there be no natural selection?

If some traits are more favorable, their allele frequencies increase.

Why must the population be extremely large?

Small populations experience genetic drift, changing allele frequencies randomly.

Why must there be no gene flow?

Migration of individuals brings new alleles, altering allele frequencies.

If a population of beetles has 70% green alleles (dominant) and 30% brown alleles (recessive), what is p?

p = 0.7

What is q for the beetle population?

q = 1 - 0.7 = 0.3

How do you calculate the frequency of homozygous dominant individuals?

p² = (0.7)² = 0.49 (49%)

How do you calculate the frequency of heterozygous individuals?

2pq = 2(0.7)(0.3) = 0.42 (42%)

How do you calculate the frequency of homozygous recessive individuals?

q² = (0.3)² = 0.09 (9%)

What does it mean if the observed genotype frequencies differ from the expected values?

The population is evolving.