EXAM 2: LECTURES 17, 19 -26

Match the nutrient conditions with the appropriate cellular regulation response. 1. Both lactose and glucose present 2. Glucose present but no lactose 3. Lactose present but no glucose 4. Neither lactose nor glucose present ---CAP binds, repressor is inactive ---Repressor and CAP are inactive ---CAP binds, repressor binds ---CAP is inactive, repressor binds

1. Both lactose and glucose present: Repressor and CAP are inactive 2. Glucose present but no lactose: CAP is inactive, repressor binds 3. Lactose present but no glucose: CAP binds, repressor is inactive 4. Neither lactose nor glucose present: CAP binds, repressor binds

If transcription and translation were not coupled in bacteria, what type of regulation would be affected? ---attenuation ---riboswitches ---negative transcriptional control of repressible genes ---negative transcriptional control of inducible genes

attenuation

A mutation that results in changing a codon such that a different amino acid is specified

missense mutation

Induced mutations are the result of exposure to a __________, which can be either a physical or a chemical agent.

mutagen Induced mutations require exposure to a mutagen. Refer to section 16.01 for further information.

The lactose (lac) operon is an example of---regulation of an---operon

negative; inducible

A mutation that changes a codon encoding an amino acid to a stop codon, resulting in premature termination of polypeptide synthesis

nonsense mutation

Transformation that is induced artificially in the laboratory typically involves uptake of _________.

plasmids Transformation that is artifically induced typically employs plasmids.

Some mutations arise from the alteration of single pairs of nucleotides and from the addition or deletion of one nucleotide pair in the coding regions of a gene; these are known as _______ mutations.

point Point mutations affect only one base pair in a given location. Refer to section 16.01 for further information.

Exposure to specific antibiotics is a ________ force that helps maintain the resistance gene in a population of bacteria.

selective Resistance genes are lost if the bacteria are not exposed to the antibiotic.

A mutation that changes a codon into a different codon, but both codons specify the same amino acid; this causes no change in the resulting polypeptide

silent mutation

The stringent response occurs when bacteria are

starved for amino acids.

If the wild-type phenotype is restores by a second mutation at a different site than the original mutation, it is called a ---mutation

suppressor

The best-studied conjugative plasmid is ______ factor, which plays a major role in conjugation in E. coli.

F The first conjugative plasmid to be described is the F factor that is found in E. coli.

This i the DNA sequence that codes for a particular protein, which in turn gives rise to a specific visible trait. Examples include the PTC taste response or lack of it, albinism or normal, and Huntington's disease or a carrier for it

Genotype

The trp operon of E. coli is regulated by attenuation. If tryptophan levels are high in the cell: ---Regions 2 & 3 of the mRNA will base pair and transcription proceeds. ---Regions 3 & 4 of the mRNA will base pair and transcription proceeds. ---Regions 2 & 3 of the mRNA will base pair and transcription terminates. ---Regions 3 & 4 of the mRNA will base pair and transcription terminates.

Regions 3 & 4 of the mRNA will base pair and transcription terminates.

When the damage to an organism's DNA is so great that the normal repair mechanisms cannot repair all the damage, a global control network called the _____ response is activated.

SOS The global control network called the SOS response is activated when damage is so great that the cell is in danger of dying.

______________ mutations arise occasionally in all cells and in the absence of any added agent.

Spontaneous Spontaneous mutations arise occasionally in all cells and in the absence of any added agent. Refer to section 16.01 for further information.

Distinguish between transcriptional riboswitches and translational riboswitches by classifying the characteristics of each group: ---Riboflavin operon ---Ribsome binding inhibition ---Interrupted mRNA production ---Gram-negative bacteria ---FMN as effector ---Occlusion of the Shine-Delgarno site ---Thiamine biosynthesis operon ---Gram-positive bacteria

Translational riboswitch ---Occlusion of the Shine-Delgarno site ---Thiamine biosynthesis operon ---Gram-negative bacteria ---Ribsome binding inhibition Transcriptional riboswitch ---Riboflavin operon ---Gram-positive bacteria ---Interrupted mRNA production ---FMN as effector

Transposons can cause mutations by ---"jumping" into a gene and disrupting its function. ---replacing specific nucleotides in the original DNA. ---inducing uncontrolled binary fission.

Transposons are genetic elements capable of moving into and out of the genomes where they reside.

Classify each of the following as either horizontal or vertical gene transfer. ---Conjugation ---From parent to offspring ---Crossing-over between sister chromosomes during meiosis ---Transformation ---Transduction ---Genes from one independent mature organism transferred to another mature organism ---Fusion of gametes

Vertical Gene Transfer ---From parent to offspring ---Crossing-over between sister chromosomes during meiosis ---Fusion of gametes Horizontal Gene Transfer ---Genes from one independent mature organism transferred to another mature organism ---Conjugation ---Transduction ---Transformation

Transposable elements are important factors in the evolution of bacteria because they: ---cause lethal mutations in all cases. ---can enhance the spread of antibiotic resistance in humans. ---can transfer antibiotic resistance from one bacterial cell to another. ---allow DNA to become resistant to treatment with UV light.

can transfer antibiotic resistance from one bacterial cell to another. Transposable elements can play a role in the spread of antibiotic resistance in bacteria.

If E.coli is grown is a medium containing glucose and maltose in equal amounts, the gluose is broken down immediately followed by the maltose at a slower rate. This is an example of the use of

catabolite repression.

________________ recombination occurs wherever there are long regions of the same or similar nucleotide sequence in two DNA molecules.

homologous Homologous recombination occurs wherever there are long regions of the same or similar nucleotide sequence in two DNA molecules.

The lac repressor is finally inactivated by binding the---called---

inducer; allolactose

An example of __________ resistance is that of the cell wall-less mycoplasma's resistance to penicillin, which interferes with peptidoglycan synthesis.

inherent The two types of resistance in bacteria are inherent and acquired.

A short sequence of DNA that contains only the gene for the enzyme transposase, and is bounded at both ends by inverted repeats is known as a(n)

insertion sequence. Insertion sequences are the simplest mobile genetic elements in bacteria.

When the second mutation is at the same site as the original mutation (e.g. the same base pair in a codon), it is called a---mutation

reversion

Mutagens can be used to cause a _____________ mutation, which will restore the ability to synthesize threonine in previously isolated auxotrophs.

reversion Mutagens can be used to induce reversion mutations in auxotrophic isolates. Refer to section 16.02 for further information.

This defines how an organism appears. examples include the color of your eyes or hair, the degree and ability of taste, the quality of your vision, and a natural resistance to a particular virus

Phenotype

Hfr strains contain the F factor integrated into their ________, rather than in the __________.

chromosome; cytoplasm The F factor is integrated into the chromosome in Hfr strains.

Transformation requires the presence of a ---cell, a cell that is capable of taking up DNA and being transformed

competent

Horizontal gene transfer can occur via ---conjugation. ---mutation. ---binary fission. ---mitosis.

conjugation.

Conjugation, the transfer of DNA by direct cell-to-cell contact, depends on the presence of a---

conjugative plasmid

The most effective method by which antibiotic resistance can be decreased in bacteria is: ---development of new antibiotics. ---increase in vaccination practices. ---decrease in antibiotic use.

decrease in antibiotic use. Decreasing the use (especially misuse) of antibiotics is the most effective means to alleviate the antibiotic-resistance problem.

Some bacteria pump the drug out of the cell after it has entered, using translocases, often called _________ pumps, that expel drugs.

efflux Translocases are efflux pumps that can pump drugs out of bacterial cells.

Transformation with a linear DNA fragment may result in: ---homologous recombination. ---unsuccessful transformation. ---formation of an episome. ---either homologous recombination or unsuccessful transformation.

either homologous recombination or unsuccessful transformation. DNA fragments can be taken up and recombine with the host cell chromosome or be unsuccessful at transforming the cell. Refer to section 16.07 for further information.

Because many species are not naturally transformation competent, these bacteria must be made artificially competent by either _________ shock or exposure to calcium chloride.

electrical Microorganisms that are not transformation competent must be treated before they will take up DNA.

Transposable elements contribute to the ____________ of bacterial and archaeal chromosomes, plasmids, and other mobile genetic elements, leading to new variations on species and strains of these organisms.

evolution Transposable elements contribute to the evolution of bacterial and archaeal chromosomes.

Streptococcus pneumoniae becomes competent during the ________ phase of bacterial growth.

exponential Streptococcus pneumoniae becomes competent during the exponential phase of growth.

A mutation from wild type to a mutant form is a ---mutation

foward

A suitable detection system for detecting mutant phenotypes is known as a ___________.

screen Mutants have to be detected before they can be worked with in the laboratory. Refer to section 16.02 for further information.

When an Hfr strain participates in conjugation, bacterial genes are transferred to the recipient in either a clockwise or a counterclockwise direction around a circular chromosome, depending on the orientation of

the integrated F factor. Genes are transferred to the recipient in either a clockwise or a counterclockwise direction around a circular chromosome, depending on the orientation of the integrated F factor.

In simple transposition, the enzyme _______________ catalyzes excision of the transposable element, followed by cleavage of a new target site and ligation of the element into this site.

transposase Simple transposition is also called cut-and-paste transposition.

A fundamental aspect of gene regulation lies in the fact that mRNA molecules are ______________. Because of this trait, these molecules won't remain in the cell long after transcription has been turned off by the cell, regulating gene expression.

unstable When a gene is turned 'on,' it will encode messenger RNA (mRNA) molecules in large numbers. If these molecules had a very long lifespan, they could continue to code for proteins long after the gene had been turned 'off.' This would defeat the purpose of gene regulation mechanisms. Since mRNA molecules are fairly unstable and degrade quickly, their 'message' doesn't last long after the gene is downregulated.

In 2002, a strain of vancomycin-resistant Staphylococcus aureus was first discovered in a patient in the U.S.; this strain had undergone conjugation with ---vancomycin-resistant E. coli. ---vancomycin-resistant enterococci. ---vancomycin-resistant Enterobacter. ---vancomycin-resistant streptococci.

vancomycin-resistant enterococci. Conjugation was used by this strain to acquire the gene encoding vancomycin resistance. Refer to section 16.09 for further information.

The more prevalent form of a gene and its associated phenotype is called the---

wild type

Select all of the characteristics that apply to transcriptional riboswitches: ---An effector molecule binds directly to the mRNA to terminate transcription. ---This type of regulation depends upon the fact that transcription and translation are coupled in bacteria. ---Transcriptional riboswitches are used to regulate transcription of the E. coli trp operon. ---Transcription depends upon the folding pattern of the mRNA. ---This type of regulation is used by Gram-positive bacteria to regulate amino acid-related genes. ---This type of regulation will lead to the formation of a pause loop, which affects the RNA polymerase.

---An effector molecule binds directly to the mRNA to terminate transcription. ---Transcription depends upon the folding pattern of the mRNA. ---This type of regulation is used by Gram-positive bacteria to regulate amino acid-related genes.

DNA in cells can encode for thousands of different proteins. Why do cells require mechanisms to regulate expression of the genes that code for these proteins?

Not all proteins are needed at all times, or in equal amounts. Regulating their expression saves energy and time.