Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

17. Mutation, Repair, and Recombination

Types of Mutations

Genetics

17. Mutation, Repair, and Recombination

Types of Mutations

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2:16 minutes

Problem 3

Textbook Question

What is the difference between a transition mutation and a transversion mutation?

Verified step by step guidance

Understand that mutations are changes in the DNA sequence, and they can be classified based on the type of nucleotide change.

Recognize that a transition mutation is a type of point mutation where a purine is replaced with another purine (A ↔ G) or a pyrimidine is replaced with another pyrimidine (C ↔ T).

Identify that a transversion mutation is another type of point mutation where a purine is replaced with a pyrimidine or vice versa (A or G ↔ C or T).

Note that transitions are more common than transversions because they involve less drastic changes in the DNA structure.

Consider the implications of these mutations: transitions may have less impact on the protein function compared to transversions, which can lead to more significant changes in the amino acid sequence.

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Key Concepts

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

Transition Mutation

A transition mutation is a type of point mutation where a purine base (adenine or guanine) is replaced by another purine, or a pyrimidine base (cytosine or thymine) is replaced by another pyrimidine. This type of mutation is more common than transversion mutations and often has less impact on the protein structure, as it maintains the same class of nucleotide.

Transversion Mutation

A transversion mutation is another type of point mutation, but it involves the substitution of a purine for a pyrimidine or vice versa. This means that adenine or guanine can be replaced by cytosine or thymine, leading to a more significant change in the DNA sequence. Transversions are less frequent than transitions and can have a greater impact on the resulting protein.

Impact on Protein Function

Both transition and transversion mutations can affect protein function, but their impacts can vary. Transition mutations are often less disruptive due to the preservation of the nucleotide class, while transversions can lead to more drastic changes in amino acid sequences, potentially altering protein structure and function. Understanding these differences is crucial for predicting the effects of mutations in genetic studies.

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Related Practice

Textbook Question

Go online to the Online Mendelian Inheritance of Man (OMIM) website. Look up the following genetic conditions and answer the questions posed about them.

Go to the 'Population Genetics' section discussing the TSD gene. In a few sentences, summarize the human population in which TSD is most frequently found and give the approximate frequency of heterozygous carriers for the TSD mutation in North American Jews.

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Textbook Question

Go online to the Online Mendelian Inheritance of Man (OMIM) website. Look up the following genetic conditions and answer the questions posed about them.

Look up Tay–Sachs disease (TSD), OMIM number 272800, and give the name and abbreviation of the affected gene and the chromosome location of the gene.

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Textbook Question

For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.

Explain why cancer is almost certain to develop with the inheritance of one mutated copy of RB1.

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Textbook Question

When working on barley plants, two researchers independently identify a short-plant mutation and develop homozygous recessive lines of short plants. Careful measurements of the height of mutant short plants versus normal tall plants indicate that the two mutant lines have the same height. How would you determine if these two mutant lines carry mutation of the same gene or of different genes?

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Textbook Question

Price et al. [(1999). J. Bacteriol. 181:2358–2362] conducted a genetic study of the toxin transport protein (PA) of Bacillus anthracis, the bacterium that causes anthrax in humans. Within the 2294-nucleotide gene in 26 strains they identified five point mutations—two missense and three synonyms—among different isolates. Necropsy samples from an anthrax outbreak in 1979 revealed a novel missense mutation and five unique nucleotide changes among ten victims. The authors concluded that these data indicate little or no horizontal transfer between different B. anthracis strains.

On what basis did the authors conclude that evidence of horizontal transfer is absent from their data?

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Textbook Question

Which types of nucleotide changes (missense or synonyms) cause amino acid changes?

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Textbook Question

Explain the following processes involving chromosome mutations and cancer development.

How the chromosome mutation producing Burkitt lymphoma generates the disease.

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