microbio exam 3

The glucose effect is observed when E. coli is inoculated into a container with glucose and lactose - the result is that the initial lag phase is extended before any growth occurs. This is because the cell must create enzymes for both glucose and lactose utilization, which it utilizes simultaneously. This requires the transcription and translation of the operons that codes for the import and breakdown of both glucose and lactose

false

in an environment with a low level of glucose and a high level of lactose. assume there are no other sugars available.

adenylate cyclase will be actively catalyzing the production of cAMP

what statements are correct for all negatively regulated operons

the operon is not transcribed when a repressor is bound to the operator, an operator is part of the operon, the operon likely has a strong promoter

inducible operons are positively regulated

false

a mutation in the trp operon leader sequence has deleted region 3 of the attenuator. the cell still has regions 1,2, and 4 of the other attenuator

the cell will experience no attenuation of the trp operon, nor with the trpR repressor be able to bind and repress the operon transcription. the cell will only be able to regulate it by feedback inhibition

a mutation in the trp operon repressor has made it incapable of binding to dsDNA. what will happen to the cell with this mutation?

the cell will still be able to control trp operon expression using attenuation, the cell will still be able to control trp production because of feedback inhibition

what type of promoter would you expect the trp operon to have, strong or weak? why?

strong. the cell always needs trp around, but it wants to limit wasting resources to produce it when there is too much. it is negatively regulated (repressor), which generally means that the operon has a strong repressor

in high levels of trp, the trpE gene is still expressed and translated because attenuation only shortens the polycistrionic mRNA for the trp operon. attenuation lets the first gene in trp biosynthesis be expressed

false

DnaK can perform these functions

presents proteins that cannot fold correctly to a protease for degradation, helps partially denatured proteins refold correctly, helps correctly fold nascent proteins

the RpoH gene codes for a heat-shock sigma factor that is only translated under heat-shock conditions

false

which of these statements are correct about DNA and RNA?

thymine is found in DNA and uracil is found in RNA, an RNA primer is used to begin DNA synthesis by the DNA pol III

what does it mean for DNA to be hemimethylated

the newly synthesized strand of DNA lacks methyl groups, while the template strand has methyl groups

what joins Okazaki fragments together in bacterial DNA replication?

DNA ligase

all genes code for proteins. all genes are translated

false

what gene is responsible for DNA polymerase proofreading

DnaQ (subunit epsilon)

the holoenzyme of the RNA polymerase is used during active RNA transcription

false

which component is the last to join the initiation complex

the large ribosomal subunit

which of the following is the name of the three-base sequence in the mRNA that binds to a tRNA molecule

codon

what it meant by saying “the direction of synthesis is 5’ to 3’ for the RNA polymerase”

ribonucleic acid-triphosphates are added to the 3’ end of the elongating RNA molecule

When coding for the amino acid Argenine, the genome uses the AGA codon much more frequently than the codon AGG. what is this an example of?

codon bias

what is correct about the regulation of bacterial genes?

repressible systems have a repressor, a repressor binds to an operator, inducible systems have a repressor, a repressor is a transcription factor

when CAP is a (blank) that is activated when it is bound to (blank), CAP is important for (blank)

activator, cAMP, catabolite repression

a stem loop structure is observed in which of the following?

mRNA, rRNA, tRNA

in Aliivirbio fischeri the (blank) is highly expressed with high concentrations of (blank). This occurs when cell density is (blank) and in turn make the cells bioluminescent.

lux operon, AHL, high

DnaK can perform these functions

helps partially denatured proteins refold correctly, helps correctly fold nascent proteins, presents proteins that cannot fold correctly to a protease for degradation

If a single-strand DNA break mutation is introduced by radiation, what repair systems might be able to fix the error?

SOS repair, recombination repair

an origin of replication can never be found on a plasmid

false

why do some plasmids encode for an antitoxin specific to a toxin that is also encoded on the plasmid

this is an example of a kill function. if the plasmid is lost in a daughter cell after cell division, the antitoxin breaks down and the toxin can kill the cell. this mechanism ensures that the plasmid is not lost from the host bacterial lineage.

what region of DNA would you expect to find an inverted repeat

terminator

what is correct about Rho-dependent termination

a stem-loop in the newly synthesized single-stranded RNA is required for Rho-dependent termination, Rho-dependent termination occurs at a pause site

what is the function of the Shine-Delgarno sequence

location on mRNA that is recognized by the small subunit of the ribosome to initiate translation

which of the following genes are likely to be encoded on a plasmid

genes encoding bacteriocins, genes encoding enzymes for the degradation of an unusual substrate, genes encoding antibacterial resistance, genes encoding toxins that damage host tissues

what is true about ter sites

the ter sites help to terminate DNA replication by trapping the replisome, the ter sites are the binding sites for the Tus factor. Tus factor is protein that is permissive to replisomes in one direction, but non-permissive in the other direction. replisomes approaching from the non-permissive direction will be trapped, helping terminate DNA replication

(blank) is used to control DNA supercoiling, while (blank) is used to separate the DNA strands of the double helix in the replisome

DNA gyrase (topoisomerase), DNA helicase

what is the template strand complementary to

coding strand, single-stranded RNA that is synthesized

how does the RNA polymerase locate the promoter in bacteria

a sigma factor binds to the core enzyme and is able to identify a specific promoter region

1/multiple genes in a bacterial operon

multiple

1/multiple promoters in a bacterial operon

1

one/multiple transcription factors in a bacterial operon

one

1/multiple shine-delgarno sequences in a bacterial operon

multiple

1/multiple start codons in a bacterial operon

multiple

what is true about DNA supercoiling

requires ATP to occur, topoisomerases are enzymes that cut DNA and regulate supercoiling, negative supercoiling (underwound) is the most common type of supercoiling, it is tightly regulated by the cell to contain DNA, allow access for gene expression, and allow access for DNA replication

what would be synthesized by RNA pol using: 5’-CAGTTCGGA-3’

5’-CAGUUCGGA-3’

a point mutation can result in

a stop codon, a silent mutation, a different amino acid (missense mutation)

what type of damage to DNA does UV light do

thymine dimers

in an environment with high glucose and high lactose what is true

the lac repressor will be inactivated by a low amount of allolactose production. this will allow for some transcription of the lac operon

what is found in a positively regulated operon that is not found in a negatively regulated operon

activator binding site

allolactose is a disaccharide involved with the regulation of the lac operon. what is true about it

it binds to the lac repressor and acts as an inducer, it is a product of the beta-galactosidase

attenuation is a regulatory method that alters operon expression by making the ribosome fall off the mRNA and halt translation when it hits a stem loop. attenuation does not affect transcription and mRNA continues to be synthesized

false

in an environment with low glucose and high lactose what is true

adenylate cyclase will be actively catalyzing the production of cAMP

a mutation in the trp operon leader sequence has changed the two trp codons in domain 1 of the attenuator into two His codons. what will happen to the cell

the cell will die because no trp will be created

why does sigma32 become more abundant when a bacterial cell is put into high temperature conditions?

the promoter for RpoH is recognized by sigma70 to constitutively express the gene, RpoH functions as an RNA thermometer, an increased number of denatured proteins are bound by DnaK and GroEL

allolactose function in lac operon regulation

inducer, binds to repressor

cAMP function in lac operon regulation

inducer, binds to activator

CAP function in lac operon regulation

activator

lacZ, beta-galactosidase function in lac operon regulation

hydrolysis of lactose

lacY, beta-galactoside permease function in lac operon regulation

transporter of beta-galactosidase

lactose function in lac operon regulation

substrate

galactose function in lac operon regulation

product

what regulatory systems control transcription and translation of RpoH gene

feedback inhibition, post-translational-level controls, transcriptional-level controls

in quorum sensing, an autoinducer is an example of (blank) that binds to the (blank) in a (blank) regulated system

effector, activator, positively

what types of HGt require cell-cell contact and DNA exchange

F factor conjugation, Hfr conjugation

what is the origin of “naked” DNA

the effect a phage has in its lytic phase, after cell dies the DNA is released

what types of HGT can a prophage perform

generalized transduction, specialized transduction

HGT performed via generalized transduction required homologous recombination

true

if a genome has only one copy of each gene it is not able to perform homologous recombination to repair an error

false

F factor transfer requires homologous recombination for successful transfer of the plasmid

false

HGT never occurs in eukaryotes

false

transduction occurs between a cell that is gram positive and a cell that is gram negative

false

order the steps of natural transformation in a gram negative bacterium

1. binding of dsDNA to outer membrane protein

2. dsDNA is moved into periplasm

3. dsDNA passed thru inner membrane into cytoplasm, one stand degraded into ssDNA

4. RecA bound to ssDNA

5. homologous recombination may occur if there is sufficient similarity

Hfr cells lack tra genes found in Fertility factor plasmid

false

which of these are examples of HGT

a bacterial cell obtains plasmid-A from the environment during heat shock, a bacterial cell obtains plasmid-A via conjugation with another cell

conjugation always results in the exchange of a plasmid from a donor cell to a recipient cell

false

what is the purpose of a chi site

it is recognized by the RecBCD complex and directs RecBCD to start adding RecA proteins onto ssDNA

what structure does “strand exchange” or “strand invasion” form during homologous recombination

Holliday junction