Bi05 - Gntc rgln

epidrs's version from 2016-12-06 14:17


Question Answer
what is an operonDNA sequence containing at least 2 regulatory sites (promoter and operator), in addition to the structural genes for a protein
function of lac operonencodes proteins required to metabolize alternate sugars when glucose is not available for glycolysis IN BACTERIA
when are the lac operon genes expressedonly when glucose is not available
parts of lac operon in a sequencei gene, CAP site, promoter, operator, Z gene, Y gene, A gene
i gene encodes for lac repressor protein
what does it mean that a gene is constitutively expressedit is always active (not regulated)
which gene in lac operon is always activei gene
Z gene encodes forbeta-galactosidase (prokaryotic lactase)
Y gene encodes forlactose permease (for entry of lactose)
A gene encodes fortransacetylase
what binds to promoterRNA polymerase
what binds to operatorrepressor
what is allolactoselactose + lactose
how does allolactose work in lac operonbinds to the repressor preventing it to bind to the operator, thereby inducing gene expression
how does glucose control lac operonglucose binds to cAMP preventing the cAMP-dependent activator to bind to the CAP site, thereby repressing gene expression
function of histidine operonencodes for histidine biosynthetic pathway when histidine is not available
what is attenuationif histidine is available, transcription is terminated before RNA polymerase reaches the structural genes of histidine operon
attenuation characteristics(1) occurs in prokaryotes only (2) requires simultaneous transcription and translation (3) two potential transcription termination signals
what happens in histidine operon at high levels of histidineribosome can move quickly because it can easily find histidine to incorporate, and this allows the message to fold into a rho-independent terminator of transcription (stem and loop + poly U)
what happens in histidine operon at low levels of histidineribosome stalls at histidine codons, and since it is covering a different part of mRNA, terminator is not formed and RNA polymerase continues transcription through the structural genes
why does attenuation regulation not occur in eukaryotesbecause in eukaryotes transcription and translation are independent events and occur in different locations
effect of acetylation on chromatinfavors gene expression (+ve charge decreases and DNA loosens)
mechanism by which acetylation worksa chromatin remodeling engine binds to acetylated lysyl residues and reconfigures the DNA to expose the promoter region
effect of scaffolding proteins on chromatincondense the chromatin (favor inactive chromatin)
effect of methylation on chromatinfavors inactive chromatin
effect of phosphorylationfavors gene expression
what are response elementsDNA sequences to which activator proteins bind in eukaryotes (e.g. UPEs, enhancers, silencers)
what are upstream promoter elements (UPE)response elements located within the promoter region (close to -25 sequence)
what is enhancer/silencer regioncluster of response elements outside the promoter region
examples of UPEsCCAAT box (-75) and GC-rich sequence
CCAAT box binds which transcription factor NF-1
GC-rich sequence binds which transcription factorSP-1
location of enhancers/silencersupstream, downstream, or within an intron, upto 1000 bp away from the gene
MOA of enhancersbending of the DNA brings enhancers close to the basal promoter region
effect of silencersbind repressor proteins
what are cis regulatorsregulatory base sequences of DNA (promoter, response element, UPE, enhancer, silencer)
what are trans regulatorstranscription factors and the genes that encode for them
what is a transcription factoractivator protein that binds response elements
function of DNA-binding domain of transcription factorbinds to a specific nucleotide sequence in the promoter or response element
examples of DNA-binding domains of transcription factorszinc fingers, leucine zippers, helix turn helix, helix loop helix
function of activation domain of transcription factor(1) binds to toher transcription factors (2) interacts with RNA polymerase II to stabilize the formation of initiation complex (3) recruits chromatin-modifying histine acetylases/deacetylases
general transcription factors areNF-1, SP-1, TF-IID
zinc fingers bindsteroid hormone receptors, thyroid hormone receptors, vit A & D receptors, PPAR receptors, GC-rich sequence
leucine zippers bindcAMP response element (CRE)
function of general transcription factorsbasal transcription
SP-1 bindsGC-rich sequence
NF-1 bindsCCAAT box
TF-IID bindsTATA box
function of TF-IIDmust bind to TATA box before RNA polymerase II can bind
PPAR is peroxisome proliferator activated receptor
helix turn helix present in homeodomain proteins
rel domains present inNFkB (nuclear factor kappa beta)
function of NFkBregulation of genes of the immune system
function of homeodomain proteinsregulation of gene expression during development of fetus
function of PPARsregulation of lipid metabolism
PPAR alpha activated byfibrates
PPAR gamma activated bythiazolidinediones
activity of specific transcription factors may be regulated bysteroid hormones (cortisol) and CREB protein (glucagon)
zellweger syndrome isdeficiency of peroxisomes (defect in fatty acid efflux) causing accumulation of long chain, branched, and hydroxylated fatty acids
zellweger syndrome is also calledleukodystrophy or cerebrohepatorenal syndrome
symptoms of zellweger syndromeimpaired brain development, hypomyelination, hypotonia, hearing and vision problems, chondrodysplasia punctata (punctate calcification of cartilage), renal cysts, enlarged liver, increased blood levels of copper and iron, death in 1st year
what accumulates in refsum's diseasephytanic acid
gemfibrozil ishypolipidemic drug used for t/t of patients with elevated TGs but normal CH and LDL levels
MOA of gemfibrozilstimulates proliferation of peroxisomes and increased gene expression of lipoprotein lipase --> fatty acid oxidation
what are peroxisomessingle-membrane organelles that accomplish beta-oxidation of long and very long chain fatty acids similar to beta-oxidation pathway. They can also conduct oxidation of branched chain fatty acids and omega-oxidation of ordinary fatty acids
difference between beta oxidation pathway and peroxisome pathwayperoxisomes generate H2O2 from fatty acid oxidation
homeodomain proteins are encoded by homeobox (HOX) and paired box (PAX) genes
mode of expression of alleles of a gene on homologous chromosomesthey are coexpressed, except in (1) barr body (2) Ig chains (3) TCR loci
klein waardenburg syndrome genetic defect inPAX 3
symptoms of klein waardenburg syndromedystopia canthorum (lateral displacement of inner corner of eyes), pigmentary abnormalities (frontal white glaze of hair, patchy hypopigmentation of skin, heterochromia iridis), congenital deafness, limb abnormalities
what is holoprosencephalyfailure of separation of cerebral hemispheres into right and left halves
holoprosencephaly caused by defect in which genesonic hedgehog (SHH) gene
defect in PAX 2 causesrenal coloboma syndrome
defect in PAX 5 causeslymphoplasmacytoid lymphoma
defect in PAX 6 causesaniria, wilm's tumor
defect in PAX 8 causesfollicular thyroid carcinoma
defect in PAX 9 causescongenital absence of teeth
defect in prader willi syndromeloss of expressed region in PATERNAL chromosome 15 OR uniparental disomy
symptoms of prader willi syndromechildhood obesity, hyperphagia, hypogonadotropic hypogonadism, small hands and feet, mental retardation, hypotonia