gene regulation Flashcards
how do prokaryotes regulate the production of enzymes?
feedback inhibition or gene regulation
what is a mechanism for control of gene expression in bacteria?
the operon model
3 points about trp ?
cluster of functionally related genes which can be on or off
switch called an operator positioned with a primer
operon switched off by repressor enzyme
what does a repressor enzyme do to trp operon?
prevents gene transcription by binding to operator and blocks rna polymerase
what is a corepressor?
cooperates a repressor to switch operon off
what does a lac operon do?
hydrolyse lactose
if lactose present, a side product binds to repressor activating it and so can no longer bind so enzymes are produced for hyrolysing lactose = glucose
what is an inducible enzyme?
usually function in catabolic pathways; synthesis induced by chem signal
what is a repressible enzyme?
function in anabolic pathways
what is positive gene regulation?
when lactose is present , glucose is scarce (cAMP level high)
what is an operon composed of?
a promoter / operator and genes (upstream regulatory genes)
what are the two types of operons?
repressible trp, inducible lac
what is chromatin?
a complex of proteins and nucleic acid in nuclei
what is NCP?
nucleosome core particle
which genes are not expressed?
genes with highly packed heterochromatin
what is epigenetic inheritance?
although chromatin modifications do not alter DNA they can be passed down generations
what is a chromosome territory?
chromosome capture techniques allow identification of regions of chromosomes which interact
two parts of nuclear architecture?
loop of chromatin and transcription factories
post transcriptional mechanisms do?
allow a cell to fine tune gene expression rapidly
include RNA processing and RNA degredation
what are three mechanisms of RNA processing?
adding 5’ cap, adding ploy-a tail, removing introns
4 points about mRNA degredation?
lifespan is important
eukaryotic mrna lives longer than prokaryotic
nucleotide sequences influence lifespan
longer the lifespan, more protein made
what processing do polypeptides undergo?
cleavage and chemical modifications
what is length of protein functions regulated by?
selective degradation
what marks proteins for degradation?
ubiquitin
what degrades proteins?
proteasome
what are microRNA?
small single stranded RNA that bind to complementary sequences in mRNA
can cause degradation pf traget mRNA or sometimes block translation
what are siRNA?
small and similar to microrna , block gene expression by siRNA called rna interference
what effects do piRNA have on chromatin?
small ncRNA induce formation of heterochromatin blocking expression of parasitic DNA in genome known as transposons
