Explanation

Transitionmutant is one in which a purine is substituted by a different purine, or a pyrimidine by a different pyrimidine. Such a change involves a base pair change between a G–C pair and an A–T pair in the DNA whereas transversion results when one nitrogen base is replaced by another different type, e.g., C-G and A-T. Transcription is the formation of mRNA on DNA template.