BIOS 252 Test - associated with a particular section of DNA and...

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BIOS 252 Test

• Which term would be applied to a regulatory condition that occurs when protein is

associated with a particular section of DNA and greatly reduces transcription?–Answer negative control

• In the diagram below, what type of control, positive or negative, is operat- ing?

-{ }( )-|-structrual gene- ^ {regulatory protien} makes a transcription.–Answer positive control

• T/F Under a system of positive control, transcription does not occur unless a regulator

molecule directly stimulates RNA production.–Answer True

• T/F Under a system of negative control, genetic expression occurs unless some form of

regulator shuts off such expression.–Answer True

• Which term is used to describe enzymes that are produced only when specific substrates are

present in the environment?–Answer inducible –Answer This term best describes enzymes that are produced only when specific substrates are present in the environment to induce their production.

• Which term refers to a contiguous genetic complex that is under coordinat- ed control?

–Answer operon 1 / 4

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• Things to define

–Answer allosteric lysogen attenuation prototroph operon Cryan experiments with gut microbes 16 interaction 17 interaction

• Which of the following mutations could lead to constitutive expression of the genes of the

lac operon?–Answer A mutation in the operator sequence. Such a mutation could prevent binding of the repressor, allowing expression under all conditions.

• Which of the following best describes the biological role of the lac operon?-

–Answer It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment. The cell expends energy to produce the proteins necessary for lactose metabolism only when lactose is present.

• T/F The placement of the operator sequence between the promotor and the structural genes

is critical to the proper function of the lac operon.–Answer True.

When the repressor binds to the operator, RNA polymerase cannot transcribe the structural genes.

• In the lac operon, the product of structural gene lacZ is capable of

.–Answer splitting the ²-linkage of lactose

• Which term most appropriately refers to a regulatory protein in prokary- otes?

–Answer 2 / 4

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DNA binding protein

• A constitutive mutation in the lac operon may be of several types. Name two types of

constitutive mutations.–Answer lacOc, lacI-

• T/F Regarding the lactose utilization system in E. coli, a constitutive mutant is one in which

the three enzymes are produced regardless of the presence or absence of lactose.–Answer True

• Which of the following is a neurochemical microbes in our gut can make?-

–Answer GABA

• Experiments led by Cryan's group found that

–Answer Mice fed lactobacilllus were more calm, behaviorally, when measured via a 6 minutes swim test.

• When Lyte asked, "Can bacteria cause stress in mice?" he did an experi- ment that

measured –Answer

–Answer how mice approached ledges of a maze

• T/F Dr. Lyte's inital experiments linking the microbiome to behavior were immediately

ground-breaking and game-changing for the field.–Answer False

• Which of the following terms best characterizes catabolite repression associated with the

lac operon in E. coli?–Answer positive control 3 / 4

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• T/F Lactose is an inducer of the lac operon.

–Answer True. Lactose indirectly induces or stimulates the transcription of genes involved in its metabolism.

• What would be the effect of a mutation in the lacI gene that prevented the repressor from

binding to lactose?–Answer The lac Z, Y, and A genes would not be expressed. If lactose could not bind to the repressor, the repressor would stay bound to the operator and repress the transcription of the lac Z, Y, and A genes.

• What is the role of glucose in catabolite repression?

–Answer It decreases the levels of cAMP in the cell, repressing transcription from the lac operon.Glucose decreases the levels of cAMP in the cell, preventing formation of the CAP-cAMP complexes necessary for the stimulation of transcription from the lac operon.

• For the

genotype, I + O+

Z+/ F' I - O+ Z+

which of the following should be entered into the chart?Genotype

I + O+ Z+/ F' I -

O+ Z+ I - Oc Z+/

F'I - O+ Z-

I s Oc Z+/ F'I + O+ Z+

I - O+ Z+/ F' I - O+ Z+

I+ = wild-type repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = constitutive operator (insensitive to repressor) lactose or no lactose in chart –Answer

• + (beta gal made when there is lactose)
• For the
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