RNAs (full name ribose nucleic acid, ribonucleic acid) are generally long (strand-like) molecules constructed from building-blocks called nucleotides. The nucleotides of RNA put together form a RNA strand are rather like a necklace made from different colored beads. RNAs carry out many important reactions needed for genes (that are physically located inside living cells) to be effective at directing or modifying organism behavior.

RNA is formed from DNA which serves as a template which determines in what order the “colored beads” (nucleotides) appear in the RNA “necklace.” The process of forming RNA is called transcription, and the RNA molecules emerging from the DNA template are often referred to as transcripts. RNA transcripts start at a site in DNA called a promoter. The place in the RNA strand where the transcription process stops is recognized as a special structure called the “RNA termination signal.” One type of RNA is called messenger RNA (mRNA), and this is involved in the pathway whereby information stored in DNA is used to direct the structure of proteins. Other types of RNA are present at structures called ribosomes which are minute factories that make proteins. The nucleotides “beads” in the RNA chain have ability to recognize partner beads on other RNA molecules.  This can lead to situations where two different RNA molecule strands lie next to each other in an attached structure that is called double-stranded RNA (dsRNA). dsRNA is involved in many different kinds of reaction that regulate or even silence gene activity.