Gene expression Flashcards
What is gene expression
The process where information from DNA is used in the synthesis of a functional gene product
Why is gene expression important
As all somatic cells contain all DNA so different cell types need to express different genes to perform their functions, respond to their environment and conserve energy so that genes are only expressed where and when they are needed
What is the promoter in a gene
The region that regulates gene expression
What is the RNA coding sequence of a gene
Region which is used to synthesise mRNA
What is meant by ‘position 1+’ on a gene
The transcription start site
How are positions on the gene labelled upstream and downstream from the +1 site
Upstream= - (Position before 1+ start site)
Downstream= + (position after 1+ start site)
What is a consensus sequence
Known sequence in promoter region that will be recognised by specific transcription factors
What is the regulatory promoter
Combination of consensus sequences in the promoter region that affects the level of transcription e.g.number of RNA molecules produced, by affecting the stability of basal transcription machinery
What is the core promoter
The site in the promoter region immediately upstream the transcription start site (1+) that is recognised by basal transcription machinery
What are the ‘core machinery’
RNA polymerases and proteins that form initiation complexes
What are the specific factors
proteins that induce or repress expression of selective genes
What is constitutive gene expression
Gene expression transcribed in all cells continually
What is regulated gene expression
Expression induced or repressed by specific factors
What are constitutive (unregulated) genes
‘Housekeeping’ genes that are always expressed within a cell at all times in the absence of a repressor or activator and are transcribed at a fixed rate at all times
What are inducible (regulated) genes
Genes that only need to be expressed at certain times in specific cells so their expression is induced by specific TFs
What are repressible (regulated) genes
Genes that only need to be turned off as needed, their expression is repressed by specific transcription repressors
What three levels is gene expression regulated at in eukaryotes
DNA structure, RNA level and protein level and activity
What is the function of regulatory mechanisms
Selective gene expression
How is gene expression regulated at DNA structure level
Changes in chromatin structure/ how condensed chromatin is
How is gene expression regulated at RNA level
Transcription factors, mRNA processing e.g. splicing and alternative splicing and RNA stability
How is gene expression regulated at protein level
Translation and post-translational modifications
How does chromatin regulate gene expression
Epigenetic mechanisms modify the way DNA is wrapped around histones in chromatin, genes are silenced in regions where chromatin is condensed p/ compact (heterochromatin) as RNA polymerase cannot access the gene, enzymes can modify histones or DNA to alter RNA pol access
How do transcription factors regulate gene expression
Turn on or off gene expression at certain times/ in certain cells by binding to the specific consensus sequence, which can impact RNA level/number by stabilising or recruiting RNA pol to promoter or modifying the interaction between DNA and histones
What are enhancer sequences
DNA sequences located in the gene promoter that are recognised by activators and further control transcription by triggering the bending of DNA
