In: Biology
A mutation changes the codon CAA to UAA. This is an example of __ A. transition, nonsense mutations B. transversion, silent mutations C. transition, missense mutations D. transversion, missense mutations E. transition, silent mutations F. transversion, nonsense mutations
Answer: option A. Transition, nonsense mutation.
Explanation:
Mutation causes changes in the nucleotide bases in DNA or RNA sequences. In the given mutation the codon 'CAA' changed into 'UAA'. The codon CAA codes for the amino acid residue glutamine, whereas UAA is a stop codon. The occurrence of the stop codon prior to expected stop codon due to the mutation causes premature termination of the translation process and produces truncated, non-functional and incomplete protein. This type of mutation is called nonsense mutation. Thus the mutation occurred here is nonsense mutation.
Transition represents a point mutation in which a purine residue (A and G) is mutated into another purine or a pyrimidine residue (C, U and T) to another pyrimidine residue. Transversion is also a point mutation in which a purine residue is changed to a pyrimidine residue and vice versa. In the given mutation, 'C' is changed into 'U', both are pyrimidine derivatives, hence, it is a transition.
Silent are neutral mutations which does not cause any observable effects.
Missense mutation is a type of mutation where a change in the single nucleotide results in a codon coding for different amino acid.