INTRON is a 6 letter word that starts with I.

1. A noncoding DNA sequence within a gene that is initially transcribed into messenger RNA but is later snipped out. See Coding, DNA, Messenger RNA, Transcription
2. DNA sequence that interrupts the protein-coding sequence of a gene; an intron is transcribed into RNA but is cut out of the message before it is translated into protein.
3. the DNA sequence in a eukaryotic gene that is not translated into a protein.