A bacterial gene is known to spontaneously mutate at a high frequency. A study of one mutant gene product shows that the mutant protein made is shorter than the wildtype protein by four amino acids. The wildtype gene has been cloned and sequenced. It has a region of repeated sequences that code alternately for proline and threonine (see below).
Met Pro Thr Pro Thr ..........
5'...ATG.........CCC ACG CCC ACG CCC ACG CCC ACG CCC ACG.......TGA....3'
a) Clearly explain, using diagrams, how a deletion of four codons could occur in this region and be passed on to progeny.
b) Is an insertion of four codons possible? Is an insertion of five codons possible? Explain why or why not in each case