Question

Which of the following mutations would cause the most harmful effect: 1) a single base insertion near the beginning of the coding sequence or 2) a three base deletion towards the end of the coding sequence.

Answer 1

Insertion of single base at beginning will cause most harmful effect because insertion of base causes change in nucleotide sequence and change reading frame i.e. create frameshift mutation which may result in change amino acid sequence in protein which produce complete different protein or or inactive protein or may be there is no translation due to missing start sequence. But if insertion at last it may cause change in hardly 1 or two amino acid sequence.