transcription process Flashcards
where does it begin
Transcription begins when an enzyme call RNA polymerase attaches to the template DNA strand and begins to catalyse the production of complementary RNA.
what are polymeerases?
= large enzymes composed of a dozen subunits and when active on DNA they are usually complexed with other factors
In eukaryotic cells – 3 types of RNA polymerase
?
RNA pol I
RNA pol II
RNA pol III
RNA pol I
transcribe the genes that encode most of the ribosomal RNAs (rRNAs)
RNA pol II
transcribes the messenger RNA (template for production of proteins)
RNA pol III
transcribes the genes for one small rRNA, plus the transfer RNAs that play key role in translation and other small regulatory RNA
Initiation:
RNA polymerase attaches to the DNA and moves along the molecule until it recognises a promoter sequence
Promoter sequence
starting point of transcription
what are transcription factors
are proteins that control the rate of transcription and also bind to the promoter sequences with RNA polymerase
Initiation: promotor I
In eukaryotes there is a ‘core promoter’ for a gene transcribed by RNA pol II
Initiation: promotor II
Eukaryotic RNA Polymerases use a number of essential cofactors – known as Transcription factors (TF)
what does TF11D recongsie
recognises the TATA box and ensures that the correct start site is used
Transcription: Elongation
RNA polymerase ‘walks’ along one strand of DNA, the TEMPLATE STRAND, in a 3’ to 5’ direction
For each nucleotide in the template, RNA polymerase adds a matching (complementary) RNA nucleotides to the 3’ end of the RNA strand
the Top strand
is known as
Coding strand
Sense strand
what is the bottom strand known as?
Bottom strand
Template strand
Antisense strand
