Final answer:
An RNA that does not encode a polypeptide is referred to as a non-coding RNA, which can have various functions in the cell such as regulation of gene expression, structural roles in the ribosome, and protein synthesis.
Step-by-step explanation:
An RNA that does not encode a polypeptide is a non-coding RNA. Non-coding RNAs play various roles in the cell, including regulation of gene expression, RNA processing, and structural functions. Examples of non-coding RNAs include rRNA (ribosomal RNA), which forms an integral part of the ribosome's structure and is involved in protein synthesis, anRd tNAs (transfer RNAs), which are responsible for bringing amino acids to the ribosome during translation. Other non-coding RNAs such as microRNAs and long non-coding RNAs are involved in gene regulation. The primary transcript mRNA undergoes post-transcriptional modification to become a mature mRNA, which can then be translated into a protein.