what happens in Lac operon system when there is no lactose present?
Repressor(made from lacI) binds to lacO and the lac operon system and the lac Z, A, Y will not be transcribed
what happens when the lactose is present?
the isoform of lactose, allolactose will bind to the repressor sitting at lacO. this binding will make the repressor fall off of lacO and the lac operon gets turned on. now lacZ, A, Y can be transcribed to digest lactose.
Outline signaling pathway of lac operon when no glucose is present
no glucose--active adenylyl cyclase--atp converted to cAMP--binds to CRP(cAMP Receptor Protein) or CAP ( catabolite activator protein)--binds to lacP(promoter region of the lac operon system )--activate transcription for lac operon (for digesting lactose) if lactose is present.
outline the signaling pathway effecting lac operon system when glucose is present
glucose--no cAMP--inactive CRP--no transcription in the lac operon system
Very important
Describe the only condition which lac operon will be transcribed ( explain in terms of the lactose and glucose)
only when lactose is PRESENT AND glucose is ABSENT. This way the repressor will be unbound (lactose present -allowing the repressor to change confirmation and fall off of the lacO) and the promoter is bound (glucose present activating cAMP)
disrupt DNA replication, transcription and DNA repair ( not translation)
fluoroquinolones
A change in the gene expressiong and phenotype without changing the gene itself
Is it heritable?
epigenetics- yes
active/ inactive chromatin
active= euchromatin ("eu" means true)
inactive=heterochromatin
what base does mathylation occur
cytosine--yields 5 methyl cytosine
where does trans-acting factors bind to?
binds to cis-regulatory elements
where are trans-acting factors and cis-regulatory elements located from the gene to be regulated ( interms of same/ diff chromosome)
trans-acting factor genes are usually on the diff chromosome than the target gene to be controled, whereas the cis-regulatory elements are on the same chromosome as the target gene.
de novo methylase
Dnmt3 (DNA methyl transferase 3)
protein that binds to methylated cytosine
MeCP2 (methyl-cytosine binding protein)
chromatin remodeling complex, recruited to the DNA by MeCP2
deacetylate lysine residue on the histone tail---gene inactivation
Sin3a & HDAC1/2 (histone deacetylase 1/2 complex)
maintain methylase for hemi-methylated DNA
matintain transcription repression during cell division
Dnmt1
ICF (immunodeficiency centromeric instability facial anomalies syndrome) is due to the mutation in
Mnmt3b gene
Mutation in X linked gene (MeCP2) results in
Rett syndrome - more prevalent in girls
what happens to the imprinted allele
imprinting pattern depends on
it is inactivated and not expressed. depends on parental origin. Genomic imprinting has monoallelic expression pattern.
switching of globin gene is done by which DNA modification mechanism?
methylation ( at the promotor region coding for globin protein)
prader willi and angelman both involve deletion in which chromosome
chromosome 15
prader willi syndrome is due to
snrpn deletion ( MATERNAL deletion at region 2)
Angelman Syndrome is due to
Deletion in UBE3A gene ( paternal deletion in region 1)
abnormal methylation is associated with
cancers
eg. methylation of tumor supressor genes, IGF( insulin like growth receptor) can be abnormally methylated
Drugs used to treat abnormal methylation, deacetylation
5 aza cytidine, sodium butyrate
repressor proteins reduce transcription through
competition
(activator and repressor compete to bind to the enhancer sequence)
when activator cannot bind to the enhancer sequence because the repressor protein is already bound
quenching
True or False- different genes have similar cis-regulatory seq.
True
spatial and temporal coordination of gene regulation by expressing transcription factors in specific cells, particular times during embryonic development and under certain environmental conditions
cis-regulatory sequences
iron storage protein
ferritin
what happens to ferritin/ transferrin receptor coding process during high and low iron level?
high iron- increase ferritin translation, reduce transferrin receptor translation
