Okay, everyone. A nonsense mutation is what type of mutation? Okay. This is a great question to quiz yourself on the different types of mutations. Answer choice a says, a nonsense mutation causes an incorrect amino acid to be inserted into a polypeptide chain. Remember that this is not correct. This is known as a missense a missense mutation, not a nonsense mutation. Answer choice b says, a nonsense mutation causes synthesis of a polypeptide chain to be terminated prematurely. Yes. This is a nonsense mutation, and that is because the change of a nucleotide would change an amino acid to a stop codon prematurely, which means that most of the protein is not even created and that this protein will not function correctly. So this is the definition of a nonsense mutation. Let's rule out the other 2. Answer choice c says a nonsense mutation prevents the start of translation. No. It does not. Answer choice d says a nonsense mutation only affects the mRNA code, but does not affect the amino acid sequence of the polypeptide. Remember that this is called a silent mutation because you don't actually see a change in the polypeptide itself, and that's where you have one codon, which is mutated to a different codon, but both of those codons code for the same amino acid, so nothing in the protein changes. Very not dangerous mutation. A nonsense mutation, however, is very dangerous because it causes the synthesis of a polypeptide chain to be terminated prematurely because it mutates a codon that used to code for amino acid to code for a stop codon. Okay, everyone. Let's move on to our next video.

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
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
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
- Flowers
  33m
- Seeds
  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

15. Gene Expression

Mutations

General Biology

15. Gene Expression

Mutations

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Multiple Choice

A nonsense mutation:

Causes an incorrect amino acid to be inserted into a polypeptide chain.

Causes synthesis of a polypeptide chain to be terminated prematurely.

Prevents the start of translation.

Only affects the mRNA code but does not affect the amino acid sequence of the polypeptide.

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Verified step by step guidance

Understand what a nonsense mutation is: A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon, in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product.

Identify the effect of a nonsense mutation: Since a nonsense mutation introduces a stop codon, it causes the translation process to terminate prematurely, leading to an incomplete polypeptide chain.

Differentiate nonsense mutation from other mutations: Unlike missense mutations, which result in a different amino acid, or silent mutations, which do not affect the amino acid sequence, nonsense mutations directly lead to a stop in protein synthesis.

Consider the options given: Evaluate each option based on the definition and effect of a nonsense mutation. The correct option should align with the premature termination of the polypeptide chain.

Conclude with the correct understanding: The correct answer is that a nonsense mutation causes the synthesis of a polypeptide chain to be terminated prematurely, as it introduces a stop codon in the mRNA sequence.