Gene mutation and DNA repair - Induced mutations

16 important questions on Gene mutation and DNA repair - Induced mutations

What are intercalating modifiers?

Intercalating modifiers are chemical mutagens that contain flat planar structures that intercalate themselves into the double helix.

What are base analogs?

Base analogs become incorporated into daughter strands during DNA replication.

What three main types do chemical mutagens come into?

  • Base modifiers;
  • Intercalating modifiers;
  • Base analogues.
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What are base modifiers?

Base modifiers are chemical mutagens that covalently modify the structure of a nucleotide.

What are examples of intercalating modifiers?

Acridine dyers such as profvalin.

What are examples of base analogs?

5-Bromouracil (5BU) and 2-aminopurine

Does 5-bromouracil (5BU) cause a transition or a transversion?

5-bromouracil causes a transition.

What are the two main types physical mutagens come into?

  • Ionizing radiation;
  • Nonionizing radiation.

What is ionizing radiation? Also give two examples.

Ionizing radiation can alter the DNA sequence. It can penetrate deeply into biological tissues, where it produces chemically reactive molecules known as free radicals. Two examples are X-rays and gamma radiation.

What is nonionizing radiation? Also give an example.

Nonionizing radiation contains less energy than ionizing radiation, and so it penetrates only on the surface of an organism. An example is UV light.

How can UV light mutate the DNA?

The UV light causes the formation of thymine dimers. Thymine dimers do not base pair properly during DNA replication, and thus a mutation can occur.

In people, what is a common cause of thymine dimer formation and in what cell type(s) would it most be likely to occur?

Thymine dimer formation is often the result of exposure to UV light. It most commonly occurs in skin cells.

What is the mutation rate?

The mutation rate is the likelihood that a gene will be altered by a new mutation. This rate is commonly expressed as the number of new mutations in a given gene per cell mutation. The mutation rate is not a constant number.

What is the mutation frequency?

The mutation frequency is the number of mutant genes divided by the total number of copies of that gene within a population.

How does nitrous acid change the structure of bases?

Nitrous acid deaminates bases, amino groups are changed to keto groups. Deamination changes cytosine to uracil and adenine to hypoxanthine (looks like guanine).

What kind of mutagen is nitrous acid?

Nitrous acid is a chemical mutagen in the category base modifiers.

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