Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
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18. Biotechnology2h 58m
19. Genomics17m
- Genomes
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20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
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  33m
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  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

22. Evolution of Populations

The Hardy-Weinberg Principle

General Biology

22. Evolution of Populations

The Hardy-Weinberg Principle

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2:22 minutes

Problem 5

Textbook Question

In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy–Weinberg equilibrium?
a. 0.9 × 2500 = 2250
b. 2 × 0.9 × 0.1 × 2500 = 450
c. 0.9 × 0.1 × 2500 = 225
d. 0.1 x 0.1 x 2500 = 25

Verified step by step guidance

Understand that cystic fibrosis is a homozygous recessive condition, which means individuals with the condition have two recessive alleles (cc).

Recall the Hardy-Weinberg principle, which states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.

Identify the frequency of the recessive allele (c) using the given frequency of the dominant allele (C). If the frequency of the dominant allele (C) is 0.9, then the frequency of the recessive allele (c) is 1 - 0.9 = 0.1.

Calculate the expected frequency of individuals with cystic fibrosis (cc) using the formula for homozygous recessive genotype frequency: \( q^2 \), where \( q \) is the frequency of the recessive allele. Thus, \( q^2 = 0.1^2 \).

Multiply the frequency of the homozygous recessive genotype (\( q^2 \)) by the total population size to find the expected number of individuals with cystic fibrosis: \( 0.1^2 \times 2500 \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hardy-Weinberg Equilibrium

The Hardy-Weinberg equilibrium is a principle that describes a stable genetic state in a population where allele and genotype frequencies remain constant across generations, provided no evolutionary influences occur. It assumes random mating, no mutation, migration, or selection, and large population size. This model helps predict genotype frequencies using allele frequencies.

Allele Frequency

Allele frequency refers to how often an allele appears in a population's gene pool. It is expressed as a proportion or percentage of the total alleles for a particular gene. In the context of Hardy-Weinberg equilibrium, allele frequencies are used to calculate expected genotype frequencies, such as homozygous recessive conditions like cystic fibrosis.

Homozygous Recessive Condition

A homozygous recessive condition occurs when an individual has two copies of a recessive allele, resulting in the expression of a recessive trait or disorder. For cystic fibrosis, individuals must inherit two recessive alleles (cc) to exhibit the condition. Calculating the frequency of such individuals involves squaring the frequency of the recessive allele under Hardy-Weinberg equilibrium.

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Textbook Question

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?

a. gene variability = 0%; number of alleles = 0

b. gene variability = 0%; number of alleles = 1

c. gene variability = 0%; number of alleles = 2

d. gene variability > 0%; number of alleles = 2

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Textbook Question

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from

a. Genetic drift.

b. Gene flow.

c. Nonrandom mating.

d. Directional selection.

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Single strands of nucleic acids are directional, meaning that there are two different ends. What functional groups define the two different ends of a strand?

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Textbook Question

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?

a. 0.7

b. 0.49

c. 0.42

d. 0.21

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Textbook Question

In a population with two alleles, B and b, the allele frequency of b is 0.4. B is dominant to b. What is the frequency of individuals with the dominant phenotype if the population is in Hardy-Weinberg equilibrium?

a. 0.16

b. 0.36

c. 0.48

d. 0.84

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Textbook Question

Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.

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Textbook Question

Make a concept map that relates DNA's primary structure to its secondary structure. Your diagram should include deoxyribonucleotides, base-stacking interactions, purines, pyrimidines, phosphodiester linkages, DNA's primary structure, DNA's secondary structure, complementary base pairing, and antiparallel double helix.

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Textbook Question

In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype aa) have the albino phenotype. In Americans of northern European ancestry, albino individuals are present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy–Weinberg equilibrium, what is the predicted frequency of Caucasians in the United States who carry a single allele for albinism?

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