What is a gene ?
Relationship of a DNA transcriptional unit to its transcribed RNA product:
RNA is transcribed from the template strand
of
DNA. As with all
nucleic
acids syntheses, the RNA product
is transcribed 5' 
3'. The
signal for the
start of transcription is the promoter, which is 'upstream'
(that
is, 5' to) with
respect to the
sense strand
of
the DNA. The first
transcribed base is several bases downstream (that
is, 3' to) from the
promoter.
Transcription then proceeds to a signal sequence at the termination
site.
The transcribed product thus includes a 5' untranslated region (5'-UTR) upstream from the
the
begining of translation at the start codon, and a 3'-UTR downstream from the
end of
translation at the stop codon. These, like the intron regions,
will be
removed before the protein product is translated from the RNA.
3'. The
signal for the
start of transcription is the promoter, which is 'upstream'
(that
is, 5' to) with
respect to the
sense strand
of
the DNA. The first
transcribed base is several bases downstream (that
is, 3' to) from the
promoter.
Transcription then proceeds to a signal sequence at the termination
site.
The transcribed product thus includes a 5' untranslated region (5'-UTR) upstream from the
the
begining of translation at the start codon, and a 3'-UTR downstream from the
end of
translation at the stop codon. These, like the intron regions,
will be
removed before the protein product is translated from the RNA.Figure modified after © 2002 by Griffiths et al. ; text © 2011 by Steven M. Carr