Transition substitution

Definition

A transition substitution is a type of point mutation where a purine base is replaced by another purine or a pyrimidine by another pyrimidine. This mutation type affects the DNA sequence but may or may not change the encoded protein.

5 Must Know Facts For Your Next Test

1. Transition substitutions are more common than transversions.
2. Purines include adenine (A) and guanine (G), while pyrimidines include cytosine (C) and thymine (T).
3. These mutations can occur due to errors during DNA replication or exposure to mutagens.
4. Transition substitutions do not always result in altered protein function, especially if they occur in non-coding regions or result in synonymous codons.
5. DNA repair mechanisms, such as mismatch repair, can correct transition substitutions to maintain genetic integrity.

Review Questions

• What bases are involved in a transition substitution?
• Why might a transition substitution not affect the resulting protein?
• Which DNA repair mechanism can correct transition substitutions?

Related terms

Transversion Substitution: A point mutation where a purine is replaced by a pyrimidine, or vice versa.

Point Mutation: A genetic alteration where a single nucleotide base is changed, inserted, or deleted from the DNA sequence.

Mismatch Repair: A DNA repair system that corrects errors introduced during DNA replication.