Consider the following statements with regard to point mutations: 1. If a purine is replaced by another purine, it is called 'transition'. 2. If a purine is replaced by a pyrimidine, it is called 'transversion'. 3. If a pyrimidine is replaced by another pyrimidine, it is called 'transversion'. Which of the statements given above are correct?
1 and 2 only
A transition is a substitution of a purine for a purine (A<->G) or a pyrimidine for a pyrimidine (C<->T). A transversion is a substitution of a purine for a pyrimidine or vice versa. Statement 3 is therefore incorrect since pyrimidine-to-pyrimidine substitution is a transition, not a transversion, making only statements 1 and 2 correct.
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