Question

Replacement of a purine N${}_2$ base with another purine base or replacement of a pyrimidine N${}_2$ base with another pyrimidine is termed as

• A. Transition
• B. Transversion
• C. Translocation
• D. Transcription

Answer 1

The correct option is A Transition

Transition is the substitution of one type of base by other of its own type. Hence, purine is replaced with purine (adenine to guanine and vice versa) and pyrimidine is replaced with the pyrimidine (cytosine to thymine/uracil and vice versa) only; option A is correct. Substitution of purine base for a pyrimidine base or substitution of pyrimidine base for a purine base is called as transversion. Hence, adenine is replaced with thymine/ uracil and guanine with cytosine which makes option B incorrect. Rearrangement of a chromosomal segment between two non-homologous chromosomes is called translocation; option C is incorrect. Transcription is the process of synthesis of RNA using DNA template strand and is carried out by RNA polymerase; option D is incorrect.