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