Question

A point mutation which involves change A $\to$ G, C $\to$ T, C $\to$ G and T $\to$ A in DNA are

• A. Transition, Transition, Transversion, Transversion
• B. Transition, Transversion, Transition, Transversion
• C. Transversion, Transition, Transversion, Transition
• D. None of the above

Answer 1

The correct option is A Transition, Transition, Transversion, Transversion

Exchange of one nitrogenous base for another base is called as the substitution. The 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. 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. In the question; Transition replaces A (purine) to G (purine) and C (pyrimidine) to T (pyrimidine) while transversion replaces C (pyrimidine) to G (purine) and T (pyrimidine) to A(purine). The correct answer is A.