Pre-mRNA

Pre-mRNA is a single stranded RNA which has been transcribed from DNA in the nucleus, it still contains introns (non-coding sections of RNA) and so is the same length as the DNA it was transcribed from. Unlike DNA the pre-mRNA contains uracil bases instead of thymine. This pre-mRNA will later be spliced by enzymes which remove the introns creating a new, mature, shorter strand of mRNA which will then leave the nucleus to be transcribed at a ribosome.