A single nucleotide addition and a single nucleotide deletion approximately 15 sites apart in the DNA cause a protein change in sequence from

Lys–Ser–Pro–Ser–Leu–Asn–Ala–Ala–Lys  

to 

Lys–Val–His–His–Leu–Met–Ala–Ala–Lys 

a) What are the old and new mRNA nucleotide sequences?

b) Which nucleotide has been added and which has been deleted? 

 (W. D. Stansfield, Theory and Problems of Genetics. McGraw-Hill, 1969.)