Gene Regulation Flashcards
What are promotor sequences
DNA sequences that define where transcription of a gene y RNA polymerase begins
They define the direction of transcription and indicate which dna strand will be transcribed
First stage in transcription?
Initiation stage : RNA polymerase recognised the promotor and starts to transcribe
What is the second phase of transcription
Elongation stage : RNA strand is continuously growing
What is the last stage of transcription
Termination phase : RNA polymerase stops synthesis and te nascent RNA is separated from DNA template
What is a repressor
A protein that inhibits expression of a gene. It may act to prevent transcription by binding to an operator site inDNA or to prevent translation by binding to RNA
What is an operator in gene regulation
The operator is the site on DNA at which a repressor protein binds to prevent transcription from initiating at the adjacent promoter
What is a promotor sequence
A promotor is a sequence of DNA needed to turn a gene on or off
Transcription is initiated at the promotor
Usually found near the beginning of a gene the rot has binding site from transcription factor
What is a TATA box
A TATA box is a DNA sequence that indicates where a genetic sequence can be decoded
What are enhancers in eukaryotic trancription
Enhancers increase the transcription of genes
Enhancers dono act on the promotor region itself, but are bound by transcription factors
What are silencers in eukaryotic transcription
They are enhancers that repress transcription instead of increasing it
General and promotor specific transcription factors
- enteral TF are active in most cell types
- promotor specific TF can influence transcription positively or negatively
- promotor specific F may be expressed in a. Tissue specific manner
General TF
General TF bind to a DNA promotor sequence near the transcription start se and help from the transcription initiation complex
Activators
These proteins bind to genes at sites known as enhancers. Activators help determine which genes will be switched on and they seed the rate of transcription
Basal transcription factors
In response to injunctions from activators, these factors position RNA polymerase a the start of the protein coding region of a gene and send the enzyme on its way
Gene regulation at chromatin level
DNA tightly wrapped around the histones is inaccessible to RNA polymerase
Chromatin remodelling must occur to slide the nucleosomes along he DNA to expose the promotor region
