Consider the tetrapeptide Ala-Thr-Ile-Gly (N-terminal to C-terminal) and suppose each stereocentre in the chain may independently have either configuration. Threonine and isoleucine each have two stereocentres (alpha and beta carbons). Counting no symmetry, the total number of stereoisomers of this tetrapeptide is

Answer: C

Stereocentres: Ala 1, Thr 2, Ile 2, Gly 0 = 5. Number of stereoisomers

= 2^{5} = 32