Question

Consider the following segment of mRNA produced by the normal order of DNA nucleotides:

5' UCU AAG CGA GUU 3'

What is the amino acid order if an insertion mutation adds a G to the beginning of the mRNA segment?

What is the amino acid order if a deletion mutation removes the U at the beginning of the mRNA segment?

Answer 1

It is simple. You just have to look up to the codon translation table to decipher the amino acids after mutation.

One amino acid is asigned for every 3 nucleotides (or a codon). So, for the normal sequence 5' UCU AAG CGA GUU 3' the amino acid sequence is Ser Lys Arg Val (in three letter notation). If you consider the one letter notation, then the mRNA simply translates to SKRV

Now, if you insert G in the beginning, the nucleotides will shift by one position to the right, then the mRNA sequence will be 5' GUC UAA GCG AGU U.. 3'. The amino acid sequence for this mutation is Val (..Stop codon). In this case, the translation stops at GUC because after GUC the ribosome reads a stop codon (UAA) and stops the translation. So the protein sequence is simply V

For the deletion mutation, the modified mRNA sequence would be 5' CUA AGC GAG UU. 3' (the nucleotides shift to one position in the left). This would translate into Leu Ser Glu or LSE.

I have attached a copy of codon table for your reference.