Clear and orderly summary of Chapter 14 of the book "Genetics: Analysis and Principles, 6th Edition by Robert Brooker". Together with all my other summaries of Genetics I got an 8,5 for this course.
Genetics Summary Chapter 14 – Gene regulation in Bacteria
Gene regulation: level of gene expression can vary under different conditions
- Unregulated genes (constitutive genes); gene is not regulated and has
constant levels of expression. expressed all the times
- Regulated genes; major genes, so that the proteins that they encode can be
produced at proper times in proper amounts. expressed only when they
required
Advantage gene regulation; more efficient in energy use.
Gene regulation can occur at transcription, translation and posttranslation (protein
function protein)
14.1 Overview of Transcriptional Regulation
Regulatory proteins: these proteins include transcription factors
- Repressor; bind to DNA and inhibit/reduce transcription – negative control
- Activator; bind to DNA and increase transcription – positive control
Small effector molecules: bind to repressor or activator. The binding of the effector
causes conformational change in regulatory proteins
influence of protein can bind to DNA.
TENTAMEN:
- Inducer; increase transcription – inducible gene
o Bind to repressor and prevent it from
binding to DNA
o Bind to activator and cause it to bind to
DNA
- Corepressor; inhibit/reduce transcription –
repressible gene
o Bind to repressor and cause it to bind to
DNA
- Inhibitor; inhibit/reduce transcription –
repressible gene
o Bind to activator and prevent it from
binding to DNA
Genetic regulatory proteins respond with small effector molecules have 2 binding
sites.
1. Where protein binds to the DNA
2. Other is binding site for effector molecule – allosteric site
14.2 Regulation of the lac Operon – inducible (op gang brengen)
Regulated by -repressor protein -activator protein
Enzyme adaptation; an enzyme appears within living cells only after the cells has
been exposed to the substrate for that enzyme
Operon; group of 2 or more genes that are transcribed from a single promotor
function;
- Coordinate the regulate of a group of genes
, - Lac operon encodes polycistronic mRNA (poly-ORF); mRNA transcribed from
operon that encodes two or more proteins
Operon is flanked (gezocht) by a promotor.
NOT all the genes in bacteria are in operons!
The lac operon encodes proteins
Transcription unites
- Regulator gene;
o LacI; codes for a
regulatory protein = lac
repressor. Has its own i
promotor. Constituively
expressed.
- Lac operon;
o CAP site; binds the
Catabolite Activator
Protein (CAP)
o lac promotor (lacP);
binds RNA polymerase
o operator site (lacO); binds lac repressor protein.
o three protein-encoding genes (lacZ, lacY, lacA)
LacZ encodes enzyme beta-galactosidase, cleaves lactose into
galactose and glucose. Side reaction: lactose into allolactose
(regulate the lac operon)
LacY; encodes lactose permease, membrane protein required
for the active transport of lactose into the cytoplasm
LacA; encodes galactoside transacetylase, modifies lactose and
lactose analogs by attachment of hydrophobic acetyl groups.
Prevents the toxic buidup in bacterial cytoplasm by allowing
them to diffuse out of the cell
o lac terminator
Lac operon repressor
Without alllactose
Lac repressor bind to lac operator and inhibit transcription. inhibit
(verhinderen) transcription
With alllactose
Lac repressor bind NOT to the lac operator. Allolactose bind to the lac
repressor and causes a conformation change that prevents the
repressor form binding to the operator. induce transcription
Allolactose is the inducer.
Allosteric regulation; effector molecule binds to noncatalytic site on
regulatory protein and cause conformational change that regulate
function.
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