Non-coding DNA
Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, ribosomal RNA, and regulatory RNAs). Other DNA sequences are not transcribed, or give rise to RNA transcripts of unknown function. The amount of non-coding DNA varies greatly between species. For example, over 98% of the human genome is noncoding DNA, while only about 2% of a typical bacterial genome is non-coding DNA.