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The diagram below shows an mRNA molecule that encodes a protein with 202 amino acids. The start and stop codons are highlighted, and a portion of the nucleotide sequence in the early part of the molecule is shown in detail. At position 35, a single base-pair substitution in the DNA has changed what would have been a uracil (U) in the mRNA to an adenine (A).

Based on the genetic code chart above, which of the following would be the result of this single base-pair substitution?

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Genetic code is the set of rules by which the information encoded in genetic material, DNA is transcribed into mRNA by the process of transcription. This mRNA formed is later translated into amino acid sequence in the living cells.

Genetic code defines how sequences of three nucleotides, called triplet codons, code for the different amino acids. The genetic code can be depicted as follows:

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In the question, when the uracil nucleotide is replaced with adenine, the triplet codon formed will be UAA. UAA represents the termination or the stop codon. Therefore, the process of translation terminates at this site. As there is a change only at one position, and there is only replacement of one nucleotide with the other, and there is no loss of any nucleotide, it will not be a frame shift mutation.

As the amino acid sequence alters, therefore it is not a silent mutation. Therefore, it is a nonsense mutation resulting in early termination of translation.

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