Transcription Flashcards
where does transcription occur in prokaryotes?
cytoplasm
where does transcription occur in eukaryotes?
nucleus
Differences between prokaryotic and eukaryotic transcription?
cytoplasm - nucleus
coupled transcription and translation (P) - no coupling (E)
No definite phase of occurrence (P) - occurs in G1 and G2 (E)
One single RNA polymerase (P) - three RNA polymerases (E)
No initiation factors (P) - Multiple general transcription factors (GTFs)
(E)
Polycistronic (P) - Monocistronic (E)
Control elements?
non-coding DNA segments that regulate transcription by binding transcription factors
promoters?
sequences of DNA bound by the first components of the Pre-Initiation Complex
Enhancers?
distal control elements
Short nucleotide sequences that influence the rate of transcription. They may be thousands of nucleotides away from the promoter or even downstream of the gene or within an intron
Enhancers may also be bound by?
by silencers/repressor proteins
what do introns interrupt?
the coding sequences
what does a typical eukaryotic gene consist of?
consists of set of sequences that appear in mature mRNA (exons) interrupted by introns
regions between genes not expressed but…
may help with chromatin assembly, contain promoters etc.
What four steps is transcription made up of?
Initiation
Elongation
Termination
Processing
what does initiation involve?
unwinding of DNA, RNA polymerase binds to template strand via Pre-initiation complex (AKA transcriotion initiation complex)
what does elongation involve?
RNA polymerase moves along the template strand
synthesising a pre-mRNA molecule. In eukaryotes there are three RNA polymerases: I, II and III
what does termination involve?
involves the addition of additional adenine nucleotides at the 3’ of the RNA transcript (a process referred to as polyadenylation)
what does processing involve?
introns are removed and the exons are spliced together to form a mature mRNA molecule consisting of a single protein-coding sequence
