Which type of RNA is referred to as the "messenger" RNA?

Messenger RNA, commonly abbreviated as mRNA, plays a crucial role in the process of gene expression. It serves as the intermediary between the DNA in the nucleus and the ribosomes in the cytoplasm, where proteins are synthesized. During transcription, a specific segment of DNA is transcribed into mRNA, which subsequently carries the genetic information needed for assembling amino acids into a protein. This process is fundamental to cellular function and the expression of genetic traits.

In contrast, ribosomal RNA (rRNA) is a structural component of ribosomes, crucial for protein synthesis, while transfer RNA (tRNA) is responsible for bringing the appropriate amino acids to the ribosome during translation. Heteronuclear RNA (hnRNA) refers to the initial RNA transcripts that undergo processing to become mature mRNA. Thus, mRNA is specifically geared toward conveying genetic information from DNA to the ribosomes, making it the "messenger" RNA in protein synthesis.