Gene Regulation Flashcards
Do prokaryotic genomes contain introns?
No
Can transcription and translation occur simultaneously in prokaryotes?
Yes.
What mechanism allows prokaryotes to translate multiple genes from the same mRNA transcript?
Operons: clusters of genes under the control of a single promoter.
What is the lac operon?
A collection of genes that regulate the metabolism of lactose in E. coli.
What is the role of lacI?
lacI is a repressor gene that regulates binding of RNA polymerase to lacO (the operator).
How does the addition of lactose result in the subsequent metabolism of lactose?
A small amount of added lactose becomes transformed into allolactose, which is an inducer that prevents the binding of the repressor to lacO.
What is polycistronic mRNA?
mRNA that encodes multiple genes.
What is bacterial conjugation?
A mechanism of horizontal gene transfer in bacteria.
What are cis-acting elements?
Elements encoded on the same chromosome as the gene they regulate (promoters, enhancers)
What are trans-acting factors?
Factors that may be encoded on different chromosomes from the genes they influence (transcription factors, polymerases)
What is the lacI s mutation? (superrepressor)
A mutation of the repressor that cannot bind the inducer, thus lacZ (which produces b-galactosidase) is always repressed.
What is the dominance relationship between lacI alleles?
lacI s > lacI + > lacI -
What does it mean if a gene is constitutive?
The gene is always expressed.
What does it mean if a gene is inducible?
The gene can either be expressed or repressed.
Do nucleosomes inhibit transcription?
Yes, it is more difficult for polymerases to bind promoters when genetic information is tightly wrapped in nucleosomes.
What is heterochromatin?
Chromatin that is not transcriptionally active.
What is euchromatin?
Chromatin that contains sites of transcriptional activity.
What is a promoter?
It is where basal transcription factors and RNA polymerase II binds, defining the site of transcription initiation.
Do genes typically have more than one promoter?
No.
Where is the promoter located?
Upstream, very close to the coding region.
What is one example of a promoter sequence?
A TATA box.
What is an enhancer?
A region containing binding sites for many different transcription factors allowing for finely tuned transcription.
Where are enhancers located?
Either upstream or downstream of the gene, sometimes thousands of kb away.
Can one enhancer influence the expression of more than one gene?
Yes.
