Study Unit 7: Control of gene expression in Bacteria
1) Simplest form of a gene:
2) Importance of gene regulation:
2.1) In prokaryotes:
1. Allows adaptation to the environment
2. Optimizes energy efficiency
3. Mostly negative regulation (turning off)
4. Gene organization: genes with functional similarity are clustered together
(called operons)
2.2) In eukaryotes:
1. Allows cellular specialization/ differentiation
2. Mostly positive (turning on)
3. Individual gene control: each gene has own promoter
3) Method of gene control:
3.1) Positive control: stimulates gene expression
3.2) Negative control: inhibits gene expression
3.3) Determination of gene expression:
1. Gene expression is determined by interaction between regulatory
proteins and the DNA sequence
2. Regulatory proteins contain amino acid sequence that can bind to DNA
3. Direct effect: regulatory protein binds directly to DNA
4. Indirect effect: regulatory protein recruits other proteins to interfere with
gene expression
3.4) DNA-binding proteins:
1. Large domains (60-90 base pairs) that form hydrogen bonds with DNA
, 2. Motif: structure within the binding domain of regulatory protein that fit
into the major groove of DNA
3. DNA-binding proteins classified by their motifs
5) Operons in Bacteria:
5.1) Introduction:
1. Structural genes clustered together and controlled by a single promoter,
transcribed together as 1 polycistronic mRNA
2. Polycistronic mRNA: mRNA that contains open reading frames for
multiple proteins
5.2) Operon contains:
1. Single promoter and terminator
2. Operator: sequence that controls gene expression (site where regulatory
proteins bind)
3. Structural genes
1) Simplest form of a gene:
2) Importance of gene regulation:
2.1) In prokaryotes:
1. Allows adaptation to the environment
2. Optimizes energy efficiency
3. Mostly negative regulation (turning off)
4. Gene organization: genes with functional similarity are clustered together
(called operons)
2.2) In eukaryotes:
1. Allows cellular specialization/ differentiation
2. Mostly positive (turning on)
3. Individual gene control: each gene has own promoter
3) Method of gene control:
3.1) Positive control: stimulates gene expression
3.2) Negative control: inhibits gene expression
3.3) Determination of gene expression:
1. Gene expression is determined by interaction between regulatory
proteins and the DNA sequence
2. Regulatory proteins contain amino acid sequence that can bind to DNA
3. Direct effect: regulatory protein binds directly to DNA
4. Indirect effect: regulatory protein recruits other proteins to interfere with
gene expression
3.4) DNA-binding proteins:
1. Large domains (60-90 base pairs) that form hydrogen bonds with DNA
, 2. Motif: structure within the binding domain of regulatory protein that fit
into the major groove of DNA
3. DNA-binding proteins classified by their motifs
5) Operons in Bacteria:
5.1) Introduction:
1. Structural genes clustered together and controlled by a single promoter,
transcribed together as 1 polycistronic mRNA
2. Polycistronic mRNA: mRNA that contains open reading frames for
multiple proteins
5.2) Operon contains:
1. Single promoter and terminator
2. Operator: sequence that controls gene expression (site where regulatory
proteins bind)
3. Structural genes
