Gene Regulation Flashcards
Two types of positive regulation
Enhancer and Activator
Two types of negative regulation
Silencer and Repressor
What is double negative regulation
inhibiting a negative regulator
Three types of temporal regulation patterns
1) increased gene expression dependent on continued presence of signal
2) Increased gene expression transient even in presence of signal
3) Increased gene expression indefinitely after signal termination
Grouped unit of genes and regulatory elements (prokaryote)
operon
Alternative name for gene (prokaryote)
cistron
Multiple genes on an operon (w/ individual start/stop)
Polycistronic
Gene comes on in presence of signal
inducible
Gene expression which is always on
constitutive expression
LacZ codes for…
beta-galactosidase
LacY codes for…
permease
LacA codes for…
transacetylase
LacI codes for…
the repressor
Inducers which bind to the repressor (inactivating it) in the lac operon…
Lactose, allactose, isopropylthiogalactoside (IPTG)
Which of the lac operon genes is constitutive?
LacI (repressor)
What happens to the lac operon in the presence of glucose?
Low levels of cAMP. cAMP not bound to CAP in order to promote lac mRNA expression
What happens to the lac operon in scare glucose conditions?
cAMP binds to CAP. CAP promotes expression of more lac mRNA
Lysogenic phase of viral reproduction
Incorporation into host bacterium’s genome
Lytic phase of viral reproduction
Destruction of the host cell while copying viral DNA
Genetic switch of bacteriophage, what breaks down the constitutive repressor?
recA
What triggers recA in the example given?
UV radiation
Cis elements in gene regulation
in the immediate vicinity of the promoter/gene
trans elements in gene regulation
coded elsewhere from the gene (usually something like a transcription factor)
Heritable changes in gene expression that occur without a change in DNA sequence
epigenetics
The three epigenetic mechanisms
1) DNA methylation
2) histone modifications
3) RNA-mediated epigenetic regulation
What enzyme methylates cytosines in DNA?
DNA methyltransferase (DNMT1)
What is methylated cytosine called
5-methylcytosine 5mC
Where is DNA methylation common?
CG (or CpG) dinucleotides
Exception to DNA methylation happening evenly?
X chromosome inactivation (random in placental mammals, paternal in marsupials) and imprinting (parent of origin dependent methylation)
Regions of tightly packed nucleosomes (highly enriched for 5mC)
heterochromatin (AT rich)
Less tightly packed nucleosomes, allowing binds of RNA polymerase and regulatory proteins controlling gene expression
euchromatin (GC rich)
Why does histone acetylation increase gene expression?
It neutralizes the (+) charge on the lysine residues, which was previously electrically drawn to (-) charges on DNA.
Do histone deacetylases (HDAC) increase or decrease gene expression?
decrease
Do histone acetylases (HAT) increase or decrease gene expression?
increase
Do histone methyltransferases increase or decrease gene expression?
decrease
Mutated methyl-CpG binding protein (MECP2) causing severely disrupted neurological development and impaired motor skills. X-linked condition
Rett Syndrome
677CT polymorphism linked to altered patterns of DNA methylation. Increased risk for breast and colorectal cancer
Methylenetetrahydrofolate reductase (MTHFR)
Imprinting disorder on Chromosome 15, leading to paternal LOF
Prader-Willi syndrome
Imprinting disorder on Chromosome 15, leading to maternal LOF
Angelman syndrome
Activation of igf2 (insulin-like growth factor) on chromosome 11
Bechwith-Wiedermann syndrome
Histone modification defect leading to severe retardation
Coffin-Lowry Syndrome
Defect in DNA methylation leading to intellectual disability
Fragile X syndrome
Two ways epigenetics leads to cancer
1) oncogenes upregulated (hypomethylation)
2) downregulation of tumor suppressor genes (hypermethylation)
Gene which checks genome for errors. It is hypermethylated in many cancers
p53
What structure / protein complex brings genes closer and could possibly play a role in gene coordination
Enhanceosomes
Three DNA binding motifs active in transcriptional control
1) zinc fingers
2) helix-turn-helix
3) leucine zipper
Three methods of transcriptional control
1) cell signaling by ligand activation of an intracellular receptor (this would cross the cell membrane)
2) ligand activation of a plasma membrane receptor (would use second messengers)
3) ligand activation of a plasma membrane G protein receptor
What processes are miRNA involved in?
early development, cell proliferation/death, fat metabolism, cell differentiation
What complex do miRNAs need to function?
RNA induced silencing complex (RISC)
How do miRNA and siRNA differ?
1) siRNA are manmade
2) siRNA are double-stranded RNA typically whereas miRNA loop back on themselves
Codeine is a prodrug for what active substance?
morphine
Which gene is responsible for metabolizing codeine into morphine?
CYP2D6
