"It is a capital mistake to theorize before you have all the evidence. It biases the judgment."-Sherlock Holmes in a Study of Scarlet
Back in the 1960s, scientists discovered sections of DNA that did not code for proteins. These non-coding DNA strands were assumed to be non-functional and were referred to as "junk" DNA, the presumed evolutionary remnants of ancestral organisms.1 Almost 99% of human DNA is known to be non-coding.
A little background will facilitate discussion of non-coding DNA. Information in coding DNA sequences is transcribed into mRNA (Figure 1). mRNA exits the nucleus and attaches to ribosomes, the molecular machines that generate proteins. In the ribosome, the information in the mRNA is translated into an amino acid sequence to form a protein.
Figure 1: Protein Formation from Coding DNA
The transcription of information from DNA to mRNA is where non-coding DNA is encountered (Figure 2).
Figure 2: mRNA Formation by Removal of Introns