Microbiology Test 3

What is is called when the H-bonds between two DNA strands break?

Because of ...............one strand of DNA can always be used as the template for the synthesis of another.

What three types of RNA is DNA transcribed to?

This type of RNA is simply amessenger and it is always translated to give a protein product

This RNA plays a very important role in thetranslational function of the ribosome

This RNA binds to amino acids anddelivers them to the ribosome where the polypeptide chain (that will fold intoa protein) is being translated from the mRNA code

Only mRNA, but not rRNA or tRNA
A. is composed of ribonucleotides.
B. is formed when DNA is transcribed
C. serves a functional purpose within the cell.
D. is translated to form protein product.
E. all of the above

Replication of a circular chromosome or a plasmid always begins ata point on the plasmid called the............and can proceed in..............

Replication of the E. coli chromosomea. initiates when an RNA polymerase enzyme called Tusunwinds a short stretch of DNA.
b. originates and terminates at the same location.
c. results in the transient formation of a region of newlysynthesized DNA called the replication bubble.

Before replication begins...........unwind the helix and..............relieve the tension.

At the replication fork, a single complex called the............(containing DNA polymerases) synthesizes both the leading and lagging strands.

DNA polymerase can only synthsize DNA in the..............direction.

This enzyme is used to form small RNA primers in the first step of the synthesis of the lagging strand.

DNA polymerase requires a............in order to beigin synthesizing DNA.

Which of the following is/are true about DNAreplication?a. It starts at the origin of replication.
b. It is bidirectional
c. It requires an RNA primer to get started.
d. It is semiconservative.
e. All of the above.

5'....TATAATGCATTCGACCTAGCAATTCGGGCCGAT...3
3'....ATATTACGTAAGCTGGATCGTTAAGCCCGGCTA....
What is the sequence of the RNA transcript for the portion ofthe gene shown here?
A. 5’AAUGCAUUCGACCUAGCAAUUCGGGCCGAU...3’
B. 5’ACCTAGCAATTCGGGCCGAT....3’
C. 5’ACCUAGCAAUUCGGGCCGAU....3’
D. 5’AATGCATTCGACCTAGCAATTCGGGCCGAT....3’

RNA always looks like the..............strand of DNA except...........is replaced by............

The..........is the transcription initiation site.

In prokaryotes,there is often more than 1 gene under control of the same promoter.This is called an

Promoters are consensus sequences of nucleotides that lie..............of the gene

The...................is the subunit of...............that recognizesthe promoter

Which of the following is/are involved with theinitiation phase of transcription but not with elongation ortermination?
A. RNA polymerase
B. the sigma factor
C. the promoter
D. the hairpin loop
E. both b and c
F. both a and d

(T or F) RNA polymerase requires a primer in order tobegin transcription
True False

(T or F) A DNA template strand can betranscribed by more than one RNA polymerase enzymes ata time.
True False

Which terminal of the mRNA transcript is readily available while transcription is still taking place (the 5' or the 3')?

What are the two types of termination?

Which statement/s regarding prokaryotic translationis/are TRUE?
A. Only the coding region of an mRNA transcript istranslated to make protein.
B. The codons UUU, UUC and UUA all encode for the sameamino acid.
C. More than one codon specifies the amino acid Val.
D. all of the above
E. a and c

Where does translation occur?

tRNA's can recognize more than one codon. This is called..........

What is the Shine-Dalgarno sequence?

The ribosome binding site is typically............................from the start codon.

Which one of the following correctly summarizesthe order of events that take place during the elongationphase of translation?
1. The initiating tRNA carrying the f-Met residue is boundin the P-site.
2. The ribosome advances the distance of one codon alongthe mRNA and the initiating tRNA + f-Met leave throughthe E-site.
3. The f-Met residue is covalently bound to the amino acidcarried by the tRNA in the A-site.
4. A tRNA carrying the amino acid that corresponds to thesecond codon binds to the A-site.
A. 4, 1, 3, 2
B. 1, 3, 4, 2
C. 1, 4, 3, 2
D. 1, 2, 3, 4

In which direction is the polypeptide chainsynthesized?
a. from the carboxyl terminal to the aminoterminal.
b. from the amino terminal to the carboxylterminal.

Which of the following is / are involved in replication?
A. sigma factor
B. The Aminoacyl(A)-site
C. The promoter
D. RNA polymerase
E. DNA polymerase

Which statement about eukaryotic and prokaryoticgene expression is FALSE?
A. In eukaryotic cells only, the 5’ end of the mRNAtranscript is “capped” by the addition of a methylatedguanine derivative.
B. In eukaryotic cells more often then prokaryotic cells,approximately 200 adenines are added to the 3’ end of themRNA transcript.
C. Generally only eukaryotic genes have both coding(exons) and noncoding (introns) regions.
D. Only prokaryotic mRNAs must be transported out ofthe nucleus before they can be translated.
E. eukaryotic mRNAs are usually monocistronic whereasprokaryotic mRNAs can be either monocistronic orpolycistronic.

A gene that is always expressed is...............

What is an operon?

A................blocks transcription by binding to an operator.

A(n)..............facilitates transcription by binding to an activator binding site.

What is a corepressor?

What is an inducer? Give an example.

What are two mechanisms by which the genotype of an organism can change?

What is a neutral mutation?

What is a base substitution?

What does the addition or removal of a nucleotide lead to?

What are transposons?

What do alklylating agents do?

What are base analogs?

What are intercalating agents?

What three ways can mutants be detected?

An organism that is Trp
A. will grow on a GSA plate.
B. has a trp+ genotype.
C. is unable to synthesize the amino acidtryptophane.
D. is a prototroph

What does the Ames test do?

A student doing his summer internship at RockyMountain Labs, performs the Ames Test on a chemicalthought to be a potential carcinogen. After incubating theGSA plate, the student notes that there are many morecolonies on the plate than are seen on a negative controlplate. Which conclusion/s does the student make?
A. The chemical tested is a potential carcinogen.
B. The chemical tested is not a potential carcinogen.
C. The chemical tested is a mutagen.
D. a and c
E. b and d
F. The chemical tested is not a mutagen.

What are the three mechanisms of lateral gene transfer?

What is a recombinant cell?

Transformation, transduction and conjugation
A. a, b and c
B. a and b
C. all involve a horizontal gene transfer.
D. all involve an F-pilus.
E. all require cell-to-cell contact.
F. all involve a bacteriophage.

Which statement/s describe/s DNA-mediatedtransformation?
A. b and c
B. The process by which a cell is transduced.
C. The uptake of “naked” DNA. The DNA can be either aplasmid or a linear piece of DNA.
D. A horizontal gene transfer.
E. The transfer of DNA from one cell to another by abacteriophage.
F. a and b

Which statement/s about DNA-mediatedtransformation is/are FALSE?
A. During transformation of a bacterial cell with a linearfragment of DNA, the fragment of donor DNA sometimesreplaces a stretch of the recipient’s chromosome in twoconsecutive steps termed breakage and reunion.
B. A cell that is capable of being transformed is termed acompetent cell and although a few genera of bacteria arenaturally competent, most must be made competent usingeither a chemical treatment or electroporation.
C. During transformation of a bacterial cell with a linearfragment of DNA, a single-stranded DNA molecule istransferred from the donor to the recipient cell via the F pilus.
D. DNA-mediated transformation involves the uptake of eitherlinear or plasmid, naked DNA.

If plasmid DNA is taken up by the cell during transformation, then the plasmid remains in the...............and replicates....................

What is entry?

What is integration?

After donor DNA has integratedinto the recipient cell’s chromosome, is stable transformation alwaysaccomplished? Why?

During..................a bacteriophage (termed adefective phage) accidentally packages bacterial DNA into its capsidhead rather than phage DNA.

Which statement about generalized transduction isFALSE?
A. During generalized transduction, an error is made duringthe phage lysogenic life cycle. This error allows the phage totake a few specific bacterial genes, next to the point ofintegration, when it leaves the host chromosome.
B. During generalized transduction, a defective phage is formed. This defective phage will effectively transfer genes from a donor cell to a recipient.
C. During generalized transduction, any gene of the donor can be transferred to the recipient.
D. During generalized transduction, a phage is mistakenlypackaged with bacterial DNA.

What is conjugaion?

Which one of the following is the most important means of plasmid transfer?
A. Transduction
B. Translocation
C. Conjugation
D. Transformation

Cells that are F+ contain the............plamid.

The F- plasmid encodes for what? What is its purpose?

What are the steps of conjugation?

The F (fertility) plasmid
A. is transferred during a lateral gene transfer event called conjugation.
B. can be found only in male (donor) cells.
C. is self-transmissible and codes for the synthesis of astructure called the F pilus.
D. all of the above
E. only a and c

In lab, we worked with a strain of Staphylococcus aureus that was resistant to penicillin. Which one of thefollowing would probably be seen in this strain of S. aureus?
A. gas vesicles
B. an R plasmid
C. a lysogenic bacteriophage
D. a lytic bacteriophage
E. none of the above

Hfr cells
A. are always cells that have more than one Rplasmid.
B. can transfer part of their chromosome to arecipient cell. After this transfer the recipient cell will become F+ and will also be capable of transferring its chromosome.
C. are cells in which the F plasmid has become integrated into the chromosome.
D. have a higher propensity to take up plasmid DNA

An antimicrobial drug
A. is a chemotherapeutic agent.
B. is any chemical used to treat microbial infection.
C. that has a high therapeutic index is selectively toxic
D. all of the above.

Beta-lactam drugs
A. are most commonly thought to inhibit the enzymes responsible for forming the tetrapeptide chains betweenstrands of peptidoglycan.
B. contain a beta-lactam ring that is essential for activity.
C. include the penicillins and the cephalosporins.
D. are effective only when cells are actively growing.
E. are naturally more effective on Gram-positive cells.
F. generally have very few side effects.
G. all of the above
H. only a through c

The broad-spectrum penicillins
A. are effective against both Gram-positive and Gramnegativeorganisms.
B. are isolated directly from Penicillium chrysogenum andundergo no further modification.
C. include penicillin G and Penicillin V.
D. include ampicillin and amoxicillin.
E. a and d
F. b and c

The extended-spectrum penicillins
A. are partially synthetic.
B. b and c
C. include cephalexin.
D. are the cephalosporins.
E. a and d
F. are effective against some tough Gram-negative bacterialike Pseudomonas.