Multiple choice Which of the following arms of tRNA differentiates it into class I and class II tRNA? DHU arm Extra arm TΨC arm Anti-codon arm Reveal answer Fill a bubble to check yourself B Correct answer Explanation The length of extra arm differentiates tRNA into class I and class II types. Class I tRNA has a shorter extra arm, i.e. 3-5 base pairs long. Class II tRNA has a longer extra arm, i.e. 13-21 base pairs long.