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Campbell AP Biology Chapter 23 Flashcards
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Campbell AP Biology Chapter 23 Flashcards

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Questions and Answers

What are the basic components of the Hardy-Weinberg model?

Frequencies of two alleles in a gene pool before and after many random matings.

Which of the following statements is not a part of the Hardy-Weinberg principle?

The genotype frequencies in the offspring generation must add up to two.

The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.

True

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

<p>0.4</p> Signup and view all the answers

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

<p>0.3</p> Signup and view all the answers

Which evolutionary force consistently results in adaptive changes in allele frequencies?

<p>Selection</p> Signup and view all the answers

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2?

<p>0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively.</p> Signup and view all the answers

Which evolutionary force could create new genetic information in a population?

<p>Mutation</p> Signup and view all the answers

If 70% of the gametes produced in a fruit fly population contain the A1 allele, what proportion of the flies carry both A1 and A2?

<p>0.42</p> Signup and view all the answers

The original source of all genetic variation is _____ .

<p>mutation</p> Signup and view all the answers

Which of the following are causes of evolutionary change?

<p>genetic drift, natural selection, mutation, gene flow</p> Signup and view all the answers

Generation-to-generation change in the allele frequencies in a population is _____ .

<p>microevolution</p> Signup and view all the answers

What is an example of a homozygous genotype?

<p>AA</p> Signup and view all the answers

All the genes in a population are that population's _____.

<p>gene pool</p> Signup and view all the answers

Genetic drift is a process based on _____.

<p>the role of chance</p> Signup and view all the answers

A mutation occurs when _____.

<p>there is a change in the DNA sequence of a gene</p> Signup and view all the answers

How will the removal of tall individuals affect the human population?

<p>Alleles that promote &quot;tallness&quot; will decrease in frequency.</p> Signup and view all the answers

Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.

<p>genetic drift</p> Signup and view all the answers

The ease with which humans travel across the globe is likely to increase _____.

<p>gene flow</p> Signup and view all the answers

Homologous pairs of chromosomes are lined up independently of other such pairs during _____.

<p>metaphase I</p> Signup and view all the answers

Crossing over, resulting in an increase in genetic variation, occurs between _____.

<p>nonsister chromatids of homologous chromosomes</p> Signup and view all the answers

In human gamete production, what is the average number of crossover events per chromosome pair?

<p>2-3</p> Signup and view all the answers

Which of these gametes contain one or more recombinant chromosomes?

<p>C</p> Signup and view all the answers

In a hypothetical population of 200 cats composed of two alleles TL and TS, which statements about the population are true?

<p>Heterozygotes make up 20% of the population. Homozygotes make up 80% of the population. In the entire cat population, 60% of the alleles are TS. In the entire cat population, the frequency of the TL allele is 0.4. Assuming random mating, each gamete has a 40% chance of having a TL allele and a 60% chance of having a TS allele.</p> Signup and view all the answers

Enter the values for the expected frequency of each genotype for TLTL, TLTS, and TSTS.

<p>.16, .48, .36</p> Signup and view all the answers

In a hypothetical population of 300 wolves, which statements accurately describe the population?

<p>Expected number of wolves with the FBFB genotype is 12. Expected number of wolves with the FBFW genotype is 96. The population may be evolving because the actual number of individuals with each genotype differs from the expected number. The population is not at Hardy-Weinberg equilibrium.</p> Signup and view all the answers

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.

<p>sexual reproduction</p> Signup and view all the answers

How can you calculate the frequency of each allele in a small population of beetles?

<p>You can use the number of observed alleles and total alleles to determine frequency.</p> Signup and view all the answers

What are the three major mechanisms of evolution?

<p>Natural selection, genetic drift, and gene flow.</p> Signup and view all the answers

What percentage of a North American population is heterozygous for cystic fibrosis, assuming Hardy-Weinberg equilibrium?

<p>2%</p> Signup and view all the answers

Rabbit ear size tends to decrease as latitude increases. This is an example of _____.

<p>a cline</p> Signup and view all the answers

What genotypes would you expect to find in the offspring of two Rr parents?

<p>You would expect RR, Rr, and rr genotypes.</p> Signup and view all the answers

In a population of flowers with allele frequencies of 80% CR and 20% CW, what are the expected proportions of genotypes?

<p>64% for CRCR, 32% for CRCW, and 4% for CWCW.</p> Signup and view all the answers

If a population is in Hardy-Weinberg equilibrium, what has to happen for allele and genotype frequencies to change?

<p>Any conditions like mutations, selection, genetic drift or non-random mating must occur.</p> Signup and view all the answers

Which type of selection tends to increase genetic variation?

<p>Disruptive selection.</p> Signup and view all the answers

In a bell-shaped curve, what does the x-axis represent?

<p>The value of a particular characteristic; characteristics can include traits like size and color.</p> Signup and view all the answers

Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This results in less genetic variation in the population.

<p>False</p> Signup and view all the answers

Which kind of selection made giraffes the long-necked creatures they are today?

<p>Directional selection.</p> Signup and view all the answers

Which kind of selection is likely at work regarding the birth weight of babies?

<p>Stabilizing selection.</p> Signup and view all the answers

Which kind of selection acts on beak size in seedcrackers?

<p>Disruptive selection.</p> Signup and view all the answers

What kind of selection acts on the adult body size of small Aristelliger lizards?

<p>Stabilizing selection.</p> Signup and view all the answers

In a hypothetical population of 500 cats, what are the expected proportions of phenotypes?

<p>The expected proportions are based on Hardy-Weinberg calculations.</p> Signup and view all the answers

Study Notes

Hardy-Weinberg Principle

  • Essential for understanding allele frequencies in a population before and after random mating.
  • Genotype frequencies in offspring must add up to one, not two.
  • Assumptions include no selection, genetic drift, gene flow, mutation, and random mating.

Genotype and Allele Frequencies

  • Calculated using the formula for a hypothetical population with specified genotypes.
  • Allele frequency results indicate proportion of dominant (A1) and recessive (A2) alleles.
  • Expected genotype frequencies can be derived from known allele frequencies.

Evolutionary Mechanisms

  • Selection consistently leads to adaptive changes in allele frequencies, improving the population's fitness.
  • Genetic drift impacts small populations through random fluctuations in allele frequencies.
  • Gene flow allows for new allele introductions, counteracting genetic drift effects.

Genetic Variation

  • Mutation is the original source of genetic variation in populations.
  • Crossover events during gamete production enhance genetic diversity among offspring.

Population Dynamics

  • Microevolution refers to generation-to-generation changes in allele frequencies.
  • Conditions violating Hardy-Weinberg equilibrium indicate potential evolution in response to environmental changes.

Selection Types

  • Directional selection favors phenotypes with extreme traits; e.g., long necks in giraffes.
  • Stabilizing selection narrows the variety of traits, favoring intermediate phenotypes; e.g., birth weights of babies.
  • Disruptive selection promotes extreme traits at both ends of the spectrum while eliminating intermediates; e.g., beak sizes in seedcrackers.

Genetic Calculations

  • Percentage of heterozygous individuals can be derived from specific allele conditions (e.g., cystic fibrosis).
  • Probabilities of offspring genotypes can be calculated using basic Mendelian genetics.

Population Examples

  • Real-world scenarios, such as mutations in cat or wolf populations, illustrate principles of phenotype distribution and allele frequency calculation.
  • Specific population responses to environmental pressures show the dynamics of selection and gene flow.

Important Terminology

  • Gene pool: all genetic information within a population.
  • Cline: gradual change in a trait or allele frequency across a geographical gradient.
  • Homozygous genotype: individuals with identical alleles for a trait (e.g., AA, aa).

Key Statistics

  • Frequency calculations often result in a decimal representation indicating allele distribution within populations.
  • Evolutionary changes can be quantified by changes in allele frequency over generations.

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Test your knowledge of the Hardy-Weinberg model with these flashcards from Campbell's AP Biology, Chapter 23. Each card covers fundamental concepts, including allele frequencies and the principles of genetic equilibrium. Perfect for quick revisions before exams!

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