CJ 8 paul Flashcards
Positive Regulation
enzyme’s activity is stimulated by a regulatory molecule v.s. being shut down.
As well as getting rid of the inhibitor, an activator must also attach to the DNA to turn on the Lac operon; this is the CAP (Catabolite Activator Protein) that must also be bound in the absence of glucose; if glucose is present, CAP will not be bound to the Lac operon
an example of a negative regulation by a metabolite like tryptophan in bacteria?
for the tryptophan operon, when tryptophan levels build up, tryptophan actually binds the tryptophan repressor and then it binds to the tryptophan operator and helps shut down synthesis of tryptophan synthetic enzymes (like when you eat a protein rich meal-lots of tryptophan);
tryptophan operon has an additional level of regulation on top of tryptophan binding the tryptophan repressor
an example of positive and negative regulation by a metabolite like lactose in bacteria?
when lactose is absent, lac repressor plugs the lac operon so it stops it from producing the enzyme that breaks down lactose. When lactose is present, allolactose binds the lac repressor so genes that encode for enzymes that help breaks down lactose, so it doesn’t cover the operator and RNA polymerase ca make the mRNA for the tryptophan enzymes
genome
the total genetic information carried by a gene on a cell (or an organism)
Do all cells have a complete genome? (except mature red blood cells
all cells have a complete genome germ cells however only have a haploid genome
How many genes on average will a typical cell express?
a typical human cell expresses ~5000-15,000 genes from a total of 25,000.
Can cells change the expression of their genes based upon changing circumstances like receiving an external signal like a hormone?
yes
Can small metabolites like lactose or tryptophan affect gene expression?
Yes can provide both positive feedback and negative feedback
Can small metabolites positively or negatively affect gene expression?
yes
Gene regulatory proteins usually bind to which groove in the DNA double helix?
To the major groove
Can gene regulatory proteins form contacts with the bases?
yes, hydrogen bonds, ionic binds, hydrophobic interactions, van der waals interactions
do gene regulatory proteins ever bind as dimers?
Yes, DNA binding proteins bind in pairs; doubles the area of contact with the DNA, increasing the strength and specificity of the protein-DNA interaction
Can gene regulatory proteins form contacts With the deoxyribose sugar?
yes
Can gene regulatory proteins form contacts With the phosphate backbone?
yes
What is the initiation site in a gene?
Where RNA polymerase initiates transcription; in bacteria it is specified by the Shine Delgarno -35 and -10 DNA promoter sequences; in eukaryotes, after TBP and other tTBP-associated factors bind to the promoter and assemble a functional transcription initiation complex, then RNA polymerase is recruited and then can itself initiate transcription at a specific nucleotide
What is the definition of an operon?
a set of genes that are transcribed into a single mRNA
Is it a set of genes found in bacteria transcribed into a single mRNA?
Yes, not eukaryotes tho
f lactose is present but not glucose, what is happening with the lac operon?
The operon is on, lactose is bound to the lac inhibitor and removes it from operator and the CAP (Catabolite Activator Protein) is bound to the Lac promoter , and RNA polymerase can produce mRNA
If glucose is present and lactose is present, what is happening with the Lac operon?
The operon is not on because the CAP is not on even though lac repressor is not bound to operator (because lactose is present)
How does the lactose operon work and how is it regulated?
lac operon codes for enzymes to break lactose into glucose and galactose. Will only transcribe the enzyme if there is lactose to be broken down and no glucose
What is the preferred carbon energy source in bacteria like E.coli: glucose or lactose?
glucose
In eukaryote where do transcription regulators bind?
They can bind in the proximal promoter, distal promoter or even in the introns or downstream of the gene
Do Gene regulatory proteins disrupt the hydrogen bonding between basepairs when they bind to the major groove?
No they do not disrupt normal hydrogen binding pattern of nitrogenous bases
What is an operator
short 15 nucleotide DNA sequence within the promoter that is recognized by the transcription regulator such as the Lac represoor or the tryptophan repressor
