What term describes genomic DNA that does not encode proteins?

The term that describes genomic DNA that does not encode proteins is often referred to as "Junk DNA." This nomenclature arose from the early understanding that a significant portion of the human genome is made up of sequences that do not appear to have a direct functional role in coding for proteins. While some of this non-coding DNA may have regulatory roles or contribute to the structural architecture of the genome, a significant amount remains poorly understood.

In contrast, messenger RNA is a type of RNA that is transcribed from DNA and serves as a template for protein synthesis, making it directly related to protein coding. Exons are the segments of DNA that are expressed and ultimately translate into proteins; these are the parts of the gene that code for the protein product. Introns are non-coding sequences that are located within genes and are removed during the process of mRNA splicing before translation. While introns are indeed non-coding, the broader category that encompasses all non-protein-coding DNA, including regulatory sequences and other non-coding elements, is what led to the informal term "Junk DNA." This is why "Junk DNA" is the most appropriate term in this context.