Table of contents
- 1. Introduction to Biology2h 42m
- 2. Chemistry3h 40m
- 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
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses19m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport1h 2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System1h 10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System1h 4m
- 44. Animal Reproduction1h 2m
- 45. Nervous System1h 55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
15. Gene Expression
Mutations
Problem 6`
Textbook Question
A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved a. deletion of one nucleotide. b. alteration of the start codon. c. insertion of one nucleotide. d. substitution of one nucleotide.

1
Understand the problem: The question is asking about a mutation that does not affect the polypeptide encoded by a gene. This means the mutation is 'silent' and does not change the amino acid sequence of the resulting protein.
Review the genetic code: The genetic code is redundant, meaning multiple codons can code for the same amino acid. A substitution of one nucleotide in a codon might still result in the same amino acid being incorporated into the polypeptide. This is known as a 'silent mutation.'
Analyze the options: A deletion or insertion of one nucleotide (options a and c) would cause a frameshift mutation, altering the reading frame of the gene and likely changing the entire amino acid sequence downstream of the mutation. This would have a significant effect on the polypeptide.
Consider the start codon (option b): Alteration of the start codon would prevent the ribosome from initiating translation properly, which would have a drastic effect on the polypeptide, likely preventing its synthesis altogether.
Focus on substitution (option d): A substitution of one nucleotide could result in a silent mutation if the new codon still codes for the same amino acid. This is the most likely explanation for a mutation that has no effect on the polypeptide.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Silent Mutation
A silent mutation is a change in the DNA sequence that does not alter the amino acid sequence of the resulting polypeptide. This can occur due to the redundancy in the genetic code, where multiple codons can code for the same amino acid. Understanding silent mutations is crucial for interpreting how certain genetic changes can be phenotypically neutral.
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Types of Mutations
Types of Mutations
Mutations can be classified into several types, including substitutions, insertions, and deletions. A substitution involves replacing one nucleotide with another, while insertions and deletions add or remove nucleotides, respectively. The impact of these mutations on protein function varies, with some potentially leading to significant changes, while others may have no effect.
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Codon and Amino Acid Relationship
Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. The relationship between codons and amino acids is fundamental to understanding how genetic information is translated into functional proteins. Changes in codons can lead to different outcomes, such as silent mutations, missense mutations, or nonsense mutations, depending on the nature of the change.
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Amino Acids