tRNA size — What is the typical average length of a mature tRNA molecule (reported in nucleotides/bp)?

Introduction:
tRNAs are among the smallest functional RNAs in cells, optimized for delivery of amino acids to ribosomes. Knowing their approximate size helps interpret gels, blots, and sequencing results in molecular biology.

Given Data / Assumptions:

• Mature tRNAs are compact and heavily modified.
• Reported lengths cluster around 73–93 nucleotides depending on species and isoacceptor.
• Conventional “average” cited in texts is near 76–85 nt.

Concept / Approach:
Choose the option that best reflects the accepted average length. Values much larger (100–140) are typical of small mRNAs or snRNAs, not tRNAs; values far smaller (40) are too short to form the cloverleaf and L-shaped structures required for function.

Step-by-Step Solution:

Verification / Alternative check:
tRNA gene annotations and tRNA-seq datasets routinely report lengths near 75–90 nt with post-transcriptional CCA addition at the 3′ end, consistent with an ~80-nt average.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing tRNA with snRNA or miRNA size classes; ignoring that “bp” here tracks nucleotide count for single-stranded RNA length.

Final Answer:
≈ 80 nucleotides.