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Genes, Gene Regulation, Genetic Disease and Epigenetics
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Genes, Gene Regulation,Genetic Disease and
Epigenetics
Gene Structure
Genes
DNA- molecule that contains genetic information
Gene- entire DNA sequence required to direct protein synthesis
Gene Density
Gene Density- number of genes per mb
How does gene encode for protein?
Gene Structure
Transcriptional
Control
Control of transcription id major way protein expression is
controlled
Transcriptional Control in Bacteria
A) Constitutive expressed gene
a. Housekeeping genes
B) Regulated genes
, a. E.g. Changes in food sources- switches on genes that encode enzymes which are needed to metabolise
that sugar
b. E.g. Changes in environmental stresses- pH and temp- switches on gene that encode proteins which help
bacterium survive
Bacterial Promoters
Control of transcription most commonly occurs at
level of transcription initiation
Promoters are recognised by RNA polymerase by having a consensus (common pattern of) DNA sequence
o Hexamer (6bp) at -35 and a TATAAT sequence at -10
Bacterial RNA
polymerase
Core enzyme
o Core enzyme has general affinity for DNA- this is known as loose binding
Holoenzyme (complete enzyme)- 4 types of subunit
o αα,β,β’
αα,β,β’σ
o σ- sigma- unit ensures binding at promotor sequences only
1000X binding strength
There’s enough σ unit for 1/3 of polymerases
Transcriptional Initiation and Elongation
, Mechanism of Transcription
RNA Polymerase
Synthesises complementary RNA copy of DNA template
strand
Transcription in Bacteria
Initiation- sigma subunit needed
Elongation- core enzyme
Termination
o RNA polymerase stops termination sequence
o RNA polymerase separates
o RNA released
Mechanisms of Control
1) Use of alternative sigma factors
2) Transcriptional Regulators
Use of alternative sigma factors
e.g. Heat Shock
- σ32- induced by high temperatures
- σ32- induced by accumulation of unfolded proteins
- σ32- recognises different -35 and -10 sequence
Transcriptional Regulators
DNA binding
proteins/
transcriptional factors
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