Bio Exam 3 Practice Questions
in which scenario is the lac operon turned off and nothing is bound? (glucose and lactose)
+ glucose + lactose
in which scenario is the lac operon turned off and only the repressor is bound to the operator? (glucose and lactose)
+ glucose - lactose
in which scenario is cAMP-CAP & RNApol bound to the operon? (glucose and lactose)
- glucose + lactose
in which scenario is the lac operon turned on? (glucose and lactose)
- glucose + lactose
in which scenario is the lac operon turned off and cAMP-CAP & repressor is bound to the operon? (glucose and lactose)
- glucose - lactose
what makes up the protein component of a nucleosome?
2 tetramers of histone proteins
what protein binds to cAMP and helps to recruit RNApol to the lac operon?
CAP
true or false: the operator codes for a protein
FALSE
true or false: the second order of chromatin packing occurs when nucleosomes coil together to form a fiber that is 300nm in diameter
FALSE its 30nm in diameter
what are the components of a nucleosome?
H2A H2B H3 H4
what part of the cAMP synthesis pathway is directly inhibited by high glucose levels in a bacterial cell?
IIIGCL
what is an example of a membrane protein?
Permease
true or false: Jacob and Monod made mutations in key regions of the operon to observe phenotypes (outcomes of those mutations)
TRUE
true or false: in the absence of lactose, bacteria produce permease protein at basal (low) levels
TRUE
true or false: the catabolite in catabolite repression for the lac operon is cAMP
TRUE
what molecule creates a conformational change in the repressor protein
allolactose
what is the name of the molecule that binds to CAP to activate transcription of the lac operon?
cAMP
what molecule is inversely proportional to the amount of glucose in the cell?
cAMP
what does a partial diploid have?
chromosomal DNA (all genes) + F' plasmid with lac operon genes
does F' plasmid or chromosomal DNA have includible synthesis in the presence of allolactose
chromosomal segment
enzymes that are continuously produced are said to have a ________ expression
constitutive
what does bacteria utilize the lac operon to do?
convert lactose into glucose for energy
what does B-galactosidase break down lactose into?
galactose glucose allolactose
what is the preferred carbon/energy source in bacteria?
glucose
chromatin of eukaryotes is organized into repeating interaction with protein octomers called nucleosomes. nucleosomes are composed of which class of molecules?
histones
what type of gene is constitutively expressed?
housekeeping
what can the lacI- bind to?
its a mutant that produces a faulty repressor that can't bind to the wild-type operator
name 2 types of constitutive mutations
lacI- lacOc
what type of mutation prevents correct tetramerization of the lac operon
lacI-d
is lacIS or lacOc cis dominant?
lacOc
if there is a mutation in the lacY- gene, what will be the most 'direct' result?
lactose will not be able to enter the bacterial cell
since the wild-type lac repressor doesn't bind to the operator 100% of the time, what is the result of this?
leaky expression low-level expression of the lac operon structural genes
what was the goal of Jacob and Monod's partial diploid studies?
learn more about lac operon regulation
What term would be applied to a regulatory condition that occurs when protein is associated with a particular section of DNA and greatly reduces transcription?
negative control
fill in the blank: lacI- is unable to bind to the ________ DNA, and the lacOc removes this DNA sequence entirely. in both cases, ther operon cannot be _________.
operator turned off
the experiments by Jacob and Monod involved what type of bacterial genome?
partial diploid
which of the following terms best characterizes catabolite repression associated with the lac operon in E. coli? negative control inducible system positive control constitutive repressible system
positive control
what binds to the operator of the lac operon?
repressor
fill in the blank: There has been a mutation in the gene that produces the ________ so that it _______ bind to the operator to _________ transcription
repressor cannot operator turn off
an operon is a cluster of genes that do what?
share a common operator (controlling site) share a promoter are transcribed onto a single, polycistronic mRNA
in the lac operon, the product of structural gene lacZ is capable of what?
splitting the linkage of lactose to produce glucose and galactose
what structures compose a nucleosome?
tetramer 2(H2A) + 2(H2B) tetramer 2(H3) + 2(H4)
what can the LacIs bind to?
the wild-type operator PERMANENTLY
is lacI+ cis or trans dominant
trans
what is the metabolite that is used for repressible gene expression?
tryptophan
when lactose is first introduced into the medium, the lac operon is not induced and thus permease isn't induced. how is it possible for lactose to enter the cell before the lac operon is induced?
while the lac operon is not induced yet, there is low level (basal) expression most of the time which allows a small amount of permease to be expressed. this allows lactose to enter the cell at low levels