Do rRNAs and tRNAs have 5' caps?

Ribosomal RNA (rRNA) and transfer RNA (tRNA) do not possess 5' caps. The 5' cap is a modified guanine nucleotide that is added to the 5' end of eukaryotic messenger RNA (mRNA) during transcription. This cap serves several important functions, such as facilitating mRNA stability, aiding in the transport of mRNA out of the nucleus, and playing a crucial role in the initiation of translation.

In contrast, tRNA and rRNA are not capped in this way. tRNAs primarily have a CCA sequence at their 3' end, which is crucial for the attachment of corresponding amino acids during protein synthesis, and they are formed through different maturation processes that do not involve a 5' cap. Similarly, rRNAs, which are integral to the structure and function of ribosomes, are also processed differently and lack the addition of a 5' cap.

Therefore, stating that rRNAs and tRNAs do not have 5' caps aligns with the established understanding of RNA processing in eukaryotic cells, hence leading to the conclusion that the correct answer is that they do not possess 5' caps.