Point mutations are those mutations that affect a single base pair. The most common nucleotide mutations are substitutions, in which one base is replaced by another. These can be of two types, either transitions or transversions. Transition substitution refers to a purine or pyrimidine being replaced by a base of the same kind; for example, a purine such as adenine may be replaced by the purine guanine. Transversion substitution refers to a purine being replaced by a pyrimidine, or vice versa; for example, cytosine, a pyrimidine, is replaced by adenine, a purine. A frameshift mutation occurs due to an insertion or deletion of a base pair that are usually not in the multiples of three. It causes the transformation of the genetic code in an unreadable format or a reading frame from the location of the mutation up till the end of the gene. Related Theory Once a pollen grain lands on the stigma of a flower of its same species, it sends out a Transcription is not a mutation, but a gene regulation mechanism in which DNA forms RNA. Related Theory Point (substitution) mutations can either be of three types: 
In mutational event, when adenine is replaced by guanine. it is a case of:
NEET UG 2004 — Zoology Principles of Inheritance and Variation
In mutational event, when adenine is replaced by guanine. it is a case of:
Held on 30 Apr 2004 · Verified 9 Jul 2026.
Options
- A
frame shift mutation
- B
transcription
- C
transition
- D
transversion
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