Which of the following is an unsual nucleoside that is found in trna but not mrna?
a. adenine
b. inosine
c. proline
d. phenylalanine
e. guanine

Inosine

Explanation:

Inosine the unusual nucleoside which is found in tRNA but not in mRNA. Inosine is derived from the nucleoside adenosine, adenosine is present in mRNA, however in case of tRNA, there is deamination of adenosine and thus, inosine is formed. The enzyme that is responsible for carrying out this reaction is called as tRNA A:34 deaminases, here the position 34 indicates that the deamination takes place at position 34 of the tRNA. The formation of inosine is essential for the wobble base pairing to take place. The formation of inosine takes place when the hypoxanthine attaches to a ribose ring with the help of the beta glycosidic bond.