In this lecture you will learn:
This happens inside the nucleus of eucaryotic cells.
The transcription process involves:
RNA polymerase binds to the DNA template and recognizes the first base to be copied.
(melting) of the DNA double helix
3.Elongation (nucleotides are added to the DNA template), synthesis of RNA based on the sequence of the DNA template strand. Once the first base is added, elongation begins and RNA nucleotides add sequentially until the polymerase reaches the end of the template.
|The RNA Polymerases
RNA polymerases are among the largest and most complex protein enzymes of living organisms.
– each polymerase consist of 2 large
polypeptide subunits and about 6 to 10 smaller ones.
|"Transcription, or RNA synthesis, is the
process of creating an equivalent RNA copy of a sequence of DNA. The
first of five stages of transcription is preinitiation. In eukaryotes,
RNA polymerase, and therefore the initiation of transcription, requires
the presence of a core promoter sequence in the DNA. Promoters are
regions of DNA which promote transcription and in eukaryotes are found
some -30 to -90 base pairs (bp) upstream from the transcription start site
(TSS). Core promoters are sequences within the promoter which are essential
for transcription initiation. RNA polymerase is able to bind to core promoters
during preinitiation in the presence of various specific transcription
A common type of core promoter in eukaryotes
is a short DNA sequence known as a TATA box.
human genes lack a TATA box and use an initiator element or downstream
core promoter instead. As in other metazoans, for genes lacking a TATA
box, the initiator element (Inr) is functionally analogous, with a consensus
YYA+1NT/AYY, to direct transcription initiation. The Inr is the only
element in metazoan protein-encoding genes known to be a functional analog
of the TATA box, in that it is sufficient for directing accurate transcription
initiation in genes that lack TATA boxes. An Inr for mammalian RNA polymerase
II can be defined as a DNA sequence element that overlaps a TSS and is
You do not need to memorize this. The TATA
or core promoter sequence
What are the four steps of transcription?
In what part of the cell does transcription occur?
What sequence on the DNA is the initiator for transcription?
What is unusual about RNA polymerase?