transcription Flashcards
Transcription
Transcription = synthesis of RNA from
(template strand of) DNA
Strands of DNA
- Coding (sense) strand: stores genetic information
- Non-coding (antisense, template) strand: complementary to coding strandserves as template („pattern”) for transcription
transcription unit
-it is the functional unit of DNA
composed :
– (1) promoter: regulatory function
– (2) RNA coding region
the promoter
responsible for the regulation of transcription
• Themostimportantconsensussequencesof promoter region are:
– TATA-box (called Pribnow-box in Prokaryotes):
• Rich in T and A bases
• RNA polymerase binds tightly to this box – GC-box
• Rich in G and C bases
• RNA polymerase binds loosely to this box
– CAP-cAMP binding site (only in Prokaryotes)
• Binding of CAP-cAMP complexone of the prerequisites of transcription
Transcription start site
located between promoter and RNA coding region where transcription starts.
– „Upstream” direction
from the start site towards promoter („left”), bases found here get number minus 1, 2 etc., when mowing away from start site
„Downstream” direction
from the start site towards RNA coding region („right”), bases found here get number plus 1, 2 etc., when mowing away from start site
untranslated region
function in transporting RNA molecules and do not take part in protein synthesis.
polycistronic transcription unit
one transcription unit is composed of several genes in PROKARYOTES only
monocistronic transcription unit
one transcription unit is composed of one gene in EUKARYOTES
intron and exon
only in eukaryotes
Introns: can be found in pre-mRNA (primary transcript) only they are cut out mature mRNA contains no intron
– Exons: mature mRNA contains exons only
structure of transcription unit
promoter
transcribed region
termination signal
