Microbiology Exam 3 - Review Pt2.

Front 1

The _____ of a bacterial cell includes both the DNA of the chromosome and that of the plasmids.

Back 1

genome

Front 2

Draw the structure of DNA.

Be sure to include the 5’-phosphate and the
ribose sugar. Simply depict the bases by their letter code. Indicate the 3’
and 5’ ends of each strand and show the H-bonds and the antiparallel
nature of the two strands.

Back 2

Picture.

Front 3

When the H-bonds between two DNA strands break =

Back 3

denaturation or melting.

Front 4

True or False.

Because of the base-pairing rules, one strand of DNA can always be
used as the template for the synthesis of another.

Back 4

True

Front 5

Practice: In a DNA molecule
a. there are two antiparallel strands of nucleotides; these
strands are joined together by hydrogen bonds. One of
the nucleotide strands runs in the 5’ to 3’ direction and
the other runs in the 3’ to 5’ direction.
b. , because of the rules of base pairing, one of the
strands of DNA can always serve as the template for the
synthesis of the other strand.
c. the hydrogen bonds holding the strands of nucleotides
together can be broken in a process called denaturation
or melting.
d. all of the above.

Back 5

D.

Front 6

Practice: In what ways is RNA different than DNA?

Back 6

catzpaw



Best Answer - Chosen by Voters

RNA
Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. RNA nucleotides contain ribose rings and uracil unlike deoxyribonucleic acid (DNA), which contains deoxyribose and thymine. It is transcribed (synthesized) from DNA by enzymes called RNA polymerases and further processed by other enzymes. RNA serves as the template for translation of genes into proteins, transferring amino acids to the ribosome to form proteins, and also translating the transcript into proteins.

Comparison with DNA
Unlike DNA, RNA is almost always a single-stranded molecule and has a much shorter chain of nucleotides. RNA contains ribose, rather than the deoxyribose found in DNA (there is a hydroxyl group attached to the pentose ring in the 2' position whereas RNA has two hydroxyl groups). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Several types of RNA (tRNA, rRNA) contain a great deal of secondary structure, which help promote stability.


RNA
http://en.wikipedia.org/wiki/Rna

DNA http://en.wikipedia.org/wiki/Dna

Front 7

What are the three different types of RNA which DNA can be transcribed to?

Back 7

mRNA
rRNA
tRNA

Front 8

Define mRNA.

Back 8

This type of RNA is simply a
messenger and it is always translated to give a protein product. In contrast,
neither rRNA nor tRNA are ever translated.

Front 9

Define rRNA

Back 9

rRNA plays a very important role in the
translational function of the ribosome.

Front 10

Define tRNA

Back 10

tRNA binds to amino acids and
delivers them to the ribosome where the polypeptide chain (that will fold into
a protein) is being translated from the mRNA code.

Front 11

Practice: 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

Back 11

d. is translated to form protein product.

Front 12

Replication of a circular chromosome or a plasmid always begins where?

Back 12

at a point on the plasmid called the origin of replication.

Front 13

True or False.

Replication
proceeds from the origin of replication in both directions.

Back 13

True

Front 14

What does bidirectional mean?

Back 14

Goes in both directions from a point of origin.

Front 15

Practice: Without using your notes, try to draw the general
replication process (depict the entire plasmid). Be sure to label
the replication forks and use a different color to represent newly
synthesized DNA. This will help you to see that replication is
semi-conservative, that is, both the final DNA molecules contain
one of the original strands and one of the newly synthesized
strands.

Back 15

picture

Front 16

Replication of the E. coli chromosome.

Initiates when an RNA polymerase enzyme calledd ____ unwinds a short stretch of DNA.

Back 16

Tus

Front 17

Replication of the E. coli chromosome.

True or False.

Originates and terminates at the same location.

Back 17

True

Front 18

Replication of the E. coli chromosome.

Results in the transient formation of a region of newly synthesized DNA called ______________.

Back 18

replication bubble.

Front 19

Details of the E. coli chromosome replication process:
a. Before replication begins, __________ unwind the helix and
__________ relieve the tension.
b. At the replication fork, a single complex called the __________
(containing __________) synthesizes BOTH THE
LEADING AND LAGGING STRANDS.
c. Because it is a single complex responsible for synthesis of both
strands and because DNA polymerase can only synthesize DNA
in the __________ direction, only one strand of newly synthesized
DNA at the replication fork can be synthesized continuously ( the __________ strand). The other strand must be synthesized
discontinuously (the ________ strand).
d. The first step in the
synthesis of the lagging strand is the formation of small RNA
primers by the enzyme called __________.

e. In the next step, DNA
polymerase recognizes the free 3’OH ends of these small
primers. It then builds DNA between primers forming ___________. A second DNA polymerase removes the RNA
primers and replaces them with DNA. Finally _______ seals
the nicks between the fragments. Be sure that you understand
that DNA polymerase requires a primer in order to begin
synthesizing DNA. (It sees a free 3’OH as its starting point.)
Even the leading strand initially begins with a small RNA primer.

Back 19

a. helicases, topoisomerases
b. replisome, DNA polymerases
c. 5' - 3' direction, leading strand, lagging strand
d. primase.
e. Okazaki
fragments, DNA ligase

Front 20

Back 20

D. dCTP

Front 21

Practice: Which of the following is/are true about DNA
replication?
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.

Back 21

e. All the above.

Front 22

By convention, the top strand of DNA is always depicted in the 5’to
3’ direction. It is called the ____ or _____ strand.

Back 22

coding or plus strand

Front 23

What is the coding or plus strand?

Back 23

By convention, the top strand of DNA is always depicted in the 5’to
3’ direction. It is called the coding or plus strand.

Front 24

What direction does the coding strand go?

Back 24

5' to 3 ' direction

Front 25

What direction does the bottom strand, the coding strand, go?

Back 25

3' to 5'

Front 26

Which strand serves as the template for the synthesis of RNA?

Back 26

The coding strand (bottom strand)

3' to 5'

Front 27

What are two other terms used commonly to describe the bottom strand?

Back 27

template or minus strand.

Front 28

True or False.

Because the
lower strand serves as template for RNA synthesis, the RNA will
always look like the plus (coding) strand except that it will be made of
ribonucleotides instead of deoxyribonucleotides and U will replace T

Back 28

True.

Front 29

Back 29

tits.

Front 30

The ______ is the transcription initiation site.

Back 30

promoter.

Front 31

What is the promoter?

Back 31

The promoter is the transcription initiation site

Front 32

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

Back 32

operon

Front 33

What is an operon?

Back 33

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

Front 34

All of the genes under control of this same
promoter will be transcribed to give a single RNA known as _________.

Back 34

polygenic or
polycistronic RNA

Front 35

In eukaryotes, generally every gene has its own
promoter. Promoters are consensus sequences of nucleotides that lie
_____________ of the gene.

(upstream or downstream)

Back 35

upstream

Front 36

In eukaryotes, promoters lie in which two areas upstream of the gene?

Back 36

The -35 region and the TATA box.

Front 37

Define Sigma factor

Back 37

The sigma factor is the subunit of RNA polymerase that recognizes
the promoter.

Front 38

Practice: Which of the following is/are involved with the
initiation phase of transcription but not with elongation or
termination?
a. RNA polymerase
b. the sigma factor
c. the promoter
d. the hairpin loop
e. both b and c
f. both a and d

Back 38

e. both b and c

Front 39

Practice: (T or F) RNA polymerase requires a primer in order to
begin transcription.

Back 39

False

Front 40

RNA polymerase adds _____ ribonucleotide at a time as according
to the DNA template strand.

Back 40

one

Front 41

Practice: (T or F) A DNA template strand can be
transcribed by more than one RNA polymerase enzymes at
a time.

Back 41

True

Front 42

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

Back 42

no clue

Front 43

What are the two different types of termination?

Back 43

a. Termination due to hairpin loop formation
b. Rho-dependent termination

Front 44

Practice drawing an amino acid. Show how a second amino acid
would bond to this amino acid at the carboxyl terminal. Continue
drawing, depicting how one amino acid after another would add to
the carboxyl terminal to form a polypeptide chain! This will not be
an exam question but it’s essential to be able to visualize the
process in order to understand translation

Back 44

draw it

Front 45

What is a codon?

Back 45

A codon is a 3-nucleotide sequence

Front 46

How many possible codons are there?

Back 46

64

Front 47

What are the 3 stop codons?

Back 47

UAA, UAG, UGA

Front 48

Since there are only 20 amino acids, it must be true that more than
one codon can specify the same amino acid. We term this concept as ________.

Back 48

degeneracy.

Front 49

Info card:

AUG is the start codon, however, it is only the start codon
(encoding for f-Met) the first time it is encountered after the ribosome
binding site (Shine-Dalgarno sequence). In all other locations, this
codon simply codes for the amino acid methionine

Back 49

kk

Front 50

Practice: Which statement/s regarding prokaryotic translation
is/are TRUE?
a. Only the coding region of an mRNA transcript is
translated to make protein.
b. The codons UUU, UUC and UUA all encode for the same
amino acid.
c. More than one codon specifies the amino acid Val.
d. all of the above
e. a and c

Back 50

idk

Front 51

What do ribosomes do?

Back 51

Factories in which translation occurs.

They stabilize the mRNA
and tRNAs such that the codons of the mRNA can be read 5’ to 3’
and the corresponding tRNAs can deliver the correct amino acids. The
ribosome then catalyzes the linkage of adjacent amino acids to
eventually form a polypeptide chain

Front 52

Ribosomes stabilize the mRNA
and tRNAs such that the codons of the mRNA can be read ________ and the corresponding tRNAs can deliver the correct amino acids.

Back 52

5’ to 3’

Front 53

Describe tRNAs

Back 53

have an amino acid binding site as well as a 3-nucleotide anticodon.
The anticodon recognizes the codon and thus allows the tRNA to
deliver the correct amino acid to the ribosome where the mRNA is
being read and the polypeptide chain is being built.

Front 54

tRNAs can recognize more than one codon = “wobble”

How does
this relate to degeneracy?

Back 54

3rd position - encodes for the same amino acid

Front 55

Practice: A tRNA with an anticodon sequence of 3’ACG 5’
would recognize which codon and carry which amino acid?

Back 55

UGC = CYS

Front 56

Describe the Shine-Dalgarno sequence.

Back 56

is a ribosomal binding site in the mRNA, generally located 8 basepairs upstream of the start codon AUG. The Shine-Dalgarno sequence exists only in prokaryotes. The six-base consensus sequence is AGGAGG; in E. coli, for example, the sequence is AGGAGGU. This sequence helps recruit the ribosome to the mRNA to initiate protein synthesis by aligning it with the start codon

Front 57

Shine-Dalgarno sequence is located generally how many basepairs upstream from the start codon?

Back 57

~ 7-8

Front 58

Why does translation not occur before transcription completes in eukaryotic cells?

The opposite is true for prokaryotic cells.

Back 58

i

Front 59

Practice: Which one of the following correctly summarizes
the order of events that take place during the elongation
phase of translation?
1. The initiating tRNA carrying the f-Met residue is bound
in the P-site.
2. The ribosome advances the distance of one codon along
the mRNA and the initiating tRNA + f-Met leave through
the E-site.
3. The f-Met residue is covalently bound to the amino acid
carried by the tRNA in the A-site.
4. A tRNA carrying the amino acid that corresponds to the
second codon binds to the A-site.
a. 1, 2, 3, 4
b. 1, 3, 4, 2
c. 1, 4, 3, 2
d. 4, 1, 3, 2

Back 59

c. 1, 4, 3, 2

Front 60

What a polysome (polyribosome)?

Back 60

The same RNA can be translated by several ribosomes at
once = a polysome or polyribosome.

Front 61

Practice: In which direction is the polypeptide chain
synthesized?
a. from the carboxyl terminal to the amino
terminal.
b. from the amino terminal to the carboxyl
terminal.

Back 61

b

Front 62

Back 62

d. all of the above

Front 63

TERMINATION

When the ribosome reaches a stop codon, __________ break the bond between the tRNA and the final amino acid in the
polypeptide chain -> translation is terminated. The ribosome
falls off the mRNA and dissociates into its subunits.

Back 63

release factors

Front 64

Practice: Which of the following is / are involved in replication?
a. RNA polymerase
b. sigma factor
c. DNA polymerase
d. The Aminoacyl(A)-site
e. The promoter

Back 64

?

Front 65

Practice: Which statement about eukaryotic and prokaryotic
gene expression is FALSE?
a. In eukaryotic cells only, the 5’ end of the mRNA
transcript is “capped” by the addition of a methylated
guanine derivative.
b. In eukaryotic cells more often then prokaryotic cells,
approximately 200 adenines are added to the 3’ end of the
mRNA transcript.
c. Generally only eukaryotic genes have both coding(exons) and noncoding (introns) regions.
d. Only prokaryotic mRNAs must be transported out of
the nucleus before they can be translated.
e. eukaryotic mRNAs are usually monocistronic whereas
prokaryotic mRNAs can be either monocistronic or
polycistronic.

Back 65

c. Generally only eukaryotic genes have both coding (exons) and noncodign (introns) regions

Front 66

A gene that is always expressed is termed to be _________

Back 66

constitutive.

Front 67

Define a constitutive gene.

Back 67

A gene that is always expressed

Front 68

What does it mean for a gene to be induced?

Back 68

Some genes are usually off but
can be turned on (induced)

Front 69

What does it mean for a gene to be repressed?

Back 69

genes are usually on but can be turned off
(repressed).

Front 70

1. PROMOTER SEQUENCE:
The closer a promoter sequence is to the ideal consensus sequence, the
more ______ it is transcribed.

Back 70

frequently

Front 71

A ______ blocks transcription by binding to an operator

Back 71

repressor

Front 72

An
___________ facilitates transcription by binding to an activator binding
site.

Back 72

activator

Front 73

Repressors and activators are ________ proteins themselves. Thus,
other molecules can bind to them and affect their ability to bind to the
DNA.

Back 73

allosteric

Front 74

Some repressors can’t bind to the operator site until another
molecule (called a _______) binds to them and allows them
to bind to the operator and block transcription (e.g. the trp
operon).

Back 74

corepressor

Front 75

Some repressors bind to the operator site and block
transcription until another molecule (called an ______) binds to
the repressor and keeps it from binding to the operator site (e.g.
the lac operon).

Back 75

inducer

Front 76

Some activators cannot bind to the activator binding site until
another molecule (called on _____) binds to them (e.g. the lac
operon).

Back 76

inducer

Front 77

Which operon is under
control of both an activator and a repressor:

Back 77

The lac operon

Front 78

Practice: In lab, we inoculated a KIA tube with E. coli.
Remember that a KIA tube contains both glucose (in short
supply) and lactose (in excess). What type of growth occurs in
this tube during an overnight incubation? Explain all of the
changes that occur on the lac operon during this incubation.
(*A QUESTION OF THIS VARIETY WILL DEFINITELY BE
ON THE EXAM. MAKE CERTAIN THAT YOU ARE
COMFORTABLE DETERMINING HOW ENVIRONMENTAL
CONDITION TELL YOU THE STATE OF THE lac
OPERON!)

Back 78

i

Front 79

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

Back 79

i

Front 80

What is a neutral mutation?

Back 80

mutations that do change the amino acid

Front 81

Practice: After a base substitution, is a stable mutant formed in
the first generation?

Back 81

No

Front 82

If a mutation occurs in an essential gene and causes death under
certain conditions but not others, what is it called?

Back 82

Conditional

Front 83

*What are some other problems caused by transposons?

Back 83

i

Front 84

True or False

Nitrosoguanidine causes GC to AT transition mutations whereas,
5-bromouracil causes AT to GC transition mutations.

Back 84

True

Front 85

Nitrosoguanidine causes __ to __ transition mutations

Back 85

GC - AT

Front 86

5 - bromouracil casues __ to __ transition mutations.

Back 86

AT - GC

Front 87

Practice: Mutations are not always harmful to an
organism, in fact, sometimes they provide a selective
advantage. What are two types of selective advantages
made possible by mutation?

Back 87

drug resistance
fitness*

Front 88

Muitations can be detected in three ways. List them.

Back 88

1) By observation if they cause a visible change in
phenotype.
2) By direct selection if the mutant will grow in the
presence of some substance that the wild type cells will
not grow in the presence of (e.g streptomycin resistant
mutants)
3) By indirect selection if the mutant is an auxotrophic
mutant and needs something for growth that the
prototrophic cells do not need. Understand replica
plating = an example of an indirect selection method.

Front 89

What is indirect selection?

Back 89

if the mutant is an auxotrophic
mutant and needs something for growth that the
prototrophic cells do not need.

Front 90

What is replica plating?

Back 90

replica plating is a technique in which one or more secondary Petri plates containing different solid (agar-based) selective growth media (lacking nutrients or containing chemical growth inhibitors such as antibiotics) are inoculated with the same colonies of microorganisms from a primary plate (or master dish), reproducing the original spatial pattern of colonies. The technique involves pressing a velveteen-covered disk, and then imprinting secondary plates with cells in colonies removed from the original plate by the material. Generally, large numbers of colonies (roughly 30-300) are replica plated due to the difficulty in streaking each out individually onto a separate plate.

http://en.wikipedia.org/wiki/File:Replica-dia-w.svg

Front 91

replica
plating an example of an ____ selection method.

Back 91

indirect

Front 92

Practice: An organism that is Trpa.
is unable to synthesize the amino acid
tryptophane.
b. will grow on a GSA plate.
c. is a prototroph
d. has a trp+ genotype.

Back 92

?

Front 93

The _______ identifies potential carcinogens by testing
chemicals for their ability to cause mutation in a bacterial system.
The particular bacterial system used is a His- auxotroph of
Salmonella. Chemicals that can cause this auxotroph to revert
to the prototroph are mutagens and considered potential
carcinogens.

Back 93

Ames test

Front 94

Define auxotroph

Back 94

An organism, such as a strain of bacteria, that has lost the ability to synthesize certain substances required for its growth and metabolism as the result of mutational changes.

Front 95

Practice: A student doing his summer internship at Rocky
Mountain Labs, performs the Ames Test on a chemical
thought to be a potential carcinogen. After incubating the
GSA plate, the student notes that there are many more
colonies on the plate than are seen on a negative control
plate. 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. The chemical tested is not a mutagen.
e. a and c
f. b and d

Back 95

?

Front 96

The donor DNA called the ________ enters a recipient cell via one
of the three mechanisms of lateral gene transfer: transformation,
transduction or conjugation

Back 96

exogenote

Front 97

What are the three mechanisms of lateral gene transfer an exogenote can enter a recipient cell?

Back 97

transformation,
transduction or conjugation

Front 98

Define a recombinant cell.

Back 98

The exogenote DNA may become a
stable part of the recipient’s genome (called the endogenote) forming
a recombinant cell

Front 99

Define endogenote

Back 99

recipient’s genome (called the endogenote)

Front 100

Practice: Transformation, transduction and conjugation
a. all involve a horizontal gene transfer.
b. all involve an F-pilus.
c. all require cell-to-cell contact.
d. all involve a bacteriophage.
e. a and b
f. a, b and c

Back 100

a. all involve

Front 101

True or False

During any recombination event, DNA is transferred,
UNIdirectionally, to no more than a small fraction of the potential recipient cells.

Back 101

True

Front 102

Practice: Which statement/s describe/s DNA-mediated
transformation?
a. The uptake of “naked” DNA. The DNA can be either a
plasmid or a linear piece of DNA.
b. A horizontal gene transfer.
c. The transfer of DNA from one cell to another by a
bacteriophage.
d. The process by which a cell is transduced.
e. a and b
f. b and c

Back 102

?

Front 103

Practice: Which statement/s about DNA-mediated
transformation is/are FALSE?
a. DNA-mediated transformation involves the uptake of either
linear or plasmid, naked DNA.
b. A cell that is capable of being transformed is termed a
competent cell and although a few genera of bacteria are
naturally competent, most must be made competent using
either a chemical treatment or electroporation.
c. During transformation of a bacterial cell with a linear
fragment of DNA, the fragment of donor DNA sometimes
replaces a stretch of the recipient’s chromosome in two
consecutive steps termed breakage and reunion.
d. During transformation of a bacterial cell with a linear
fragment of DNA, a single-stranded DNA molecule is
transferred from the donor to the recipient cell via the F pilus.

Back 103

?

Front 104

After linear DNA is taken up via transformation, it may be _______. Thus although transofrmation has occured, recombination has not!

Back 104

degraded.

Front 105

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

Back 105

cytoplasm, independtly.

Front 106

If linear DNA is taken up during transformation and it is NOT degraded:


1. _______ = A double-stranded piece of DNA adheres to the cell
surface. One strand is degraded by nucleases and the other strand
enters the cell. This mechanism varies amongst different genera.
2. __________ (nonreciprocal general recombination) = The
ssDNA aligns with a region on the recipient cell’s chromosome to
which it is highly homologous. (**HIGHLY HOMOLOGOUS =
VERY SIMILAR). The recipient DNA separates and pairs with the
donor DNA. A nuclease cleaves the recipient cell’s DNA and
releases the homologous section into the cytoplasm to be degraded
by nucleases. This is called BREAKAGE. The donor DNA now
replaces the recipient DNA = REUNION. This forms a region of
heteroduplex DNA (one strand is donor DNA, the other is
recipient DNA).

Back 106

ENTRY

2. INTEGRATION

Front 107

After donor DNA has integrated
into the recipient cell’s chromosome, is stable transformation always
accomplished? Why?

Back 107

not always, sometimes the mismatch
repair system catches errors and the sequence is unchanged. There’s
a 50/50 chance in terms of which strand will be repaired.

Front 108

Transduction

During _______, a bacteriophage (termed a
defective phage) accidentally packages bacterial DNA into its capsid
head rather than phage DNA. The phage still goes along to the next
target cell but when it injects its DNA into the host cell, it only injects
bacterial DNA. This donor (exogenote) DNA now has three possible
fates: integration into the endogenote, degradation, or abortive
transduction

Back 108

generalized transduction

Front 109

What is generalized transduction?

Back 109

During generalized transduction, a bacteriophage (termed a
defective phage) accidentally packages bacterial DNA into its capsid
head rather than phage DNA. The phage still goes along to the next
target cell but when it injects its DNA into the host cell, it only injects
bacterial DNA. This donor (exogenote) DNA now has three possible
fates: integration into the endogenote, degradation, or abortive
transduction.

Front 110

What is specialized transduction?

Back 110

only a few specific genes from one bacterial cell are transferred to the second bacterial host by a phage

http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter17/animation_quiz_3.html

Front 111

Practice: Which statement about generalized transduction is
FALSE?
a. During generalized transduction, an error is made during
the phage lysogenic life cycle. This error allows the phage to
take a few specific bacterial genes, next to the point of
integration, when it leaves the host chromosome.
b. During generalized transduction, any gene of the donor can
be transferred to the recipient.
c. During generalized transduction, a phage is mistakenly
packaged with bacterial DNA.
d. During generalized transduction, a defective phage is
formed. This defective phage will effectively transfer genes
from a donor cell to a recipient.

Back 111

a. During generalized transduction, an error is made during
the phage lysogenic life cycle. This error allows the phage to
take a few specific bacterial genes, next to the point of
integration, when it leaves the host chromosome.

Front 112

Define Conjugation

Back 112

Conjugation = The transfer of DNA from a donor to a recipient cell
via cell-to-cell contact.

Front 113

Practice: Which one of the following is the most important
means of plasmid transfer?
a. Transduction
b. Conjugation
c. Transformation
d. Translocation

Back 113

C. Conjugation

Front 114

In order for a plasmid to be transferred from a donor cell to a
recipient cell via conjugation, the plasmid must have what?


Such plasmids are called selftransmissible
or conjugative (e.g. F (fertility)-plasmids and R
(resistance)-plasmids.)

Back 114

a gene
encoding for this transfer.


Such plasmids are called selftransmissible
or conjugative (e.g. F (fertility)-plasmids and R
(resistance)-plasmids.)

Front 115

Examples of plasmids that encode for their transfer

Back 115

Such plasmids are called selftransmissible
or conjugative (e.g. F (fertility)-plasmids and R
(resistance)-plasmids.)

Front 116

F+ (male, donor) or F- (female) contain the F-plasmid?

Back 116

F+

Front 117

What does the F-plasmid encode for?

Back 117

Encodes for the tF pilus which serves as a bridge over which the F plasmid can be transferred from the donor cell to the F- (female or recipient cell).

Front 118

What are the steps of conjugations?

Back 118

Contact
Mobilization
Transfer
Synthesis


The sex pilus of the donor cell binds to the
recipient cell and pulls the two cells together. This is often called
contact. Next, the bottom strand of the F-plasmid is cleaved. This
step is called mobilization. The rolling circle mechanism of
replication is used during plasmid transfer. As the bottom strand of
the original plasmid is transferred to the recipient cell, a complimentary
strand is synthesized. This step is often called synthesis. Thus, after
plasmid transfer, both the donor and recipient cell are F+.

Front 119

Practice: 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 a
structure called the F pilus.
d. all of the above
e. only a and c

Back 119

D. all the above

Front 120

________ contain genes allowing for resistance to certain
antimicrobial substances and or heavy metals. These plasmids
probably originated when transposons, carrying resistance genes,
jumped into self-transmissible plasmids.

Back 120

R-plasmids

Front 121

R-plasmids contain genes allowing for resistance to certain
____________________________.

Back 121

antimicrobial substances and or heavy metals

Front 122

Theory of R-plasmid origin?

Back 122

These plasmids
probably originated when transposons, carrying resistance genes,
jumped into self-transmissible plasmids.

Front 123

Practice: In lab, we worked with a strain of Staphylococcus
aureus that was resistant to penicillin. Which one of the
following 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

Back 123

b. an r plasmid

Front 124

Who was Paul Ehrlich?

Back 124

His life is depicted in the movie Dr. Ehrlich's Magic Bullet, which focused on Salvarsan (arsphenamine, "compound 606"), his cure for syphilis.

The concept of a "magic bullet" drug comes from the experience of 19th century German chemists with selectively staining tissues for histological examination, and in particular, selectively staining bacteria (Ehrlich was an exceptionally gifted histological chemist, and invented the precursor technique to Gram staining bacteria). Ehrlich reasoned that if a compound could be made that selectively targeted a disease-causing organism, then a toxin for that organism could be delivered along with the agent of selectivity. Hence, a "magic bullet" would be created that killed only the organism targeted.

A problem with the use of the magic bullet concept as it emerged from its histological roots is that people confused the dye with the agent of tissue selectivity and antibiotic activity. Prontosil, a sulfa drug whose active component is sulfanilamide, is a classic example of the fact that color is not essential to antibacterial activity


GERMAN PRIDE

Front 125

What are Hfr cells?

Back 125

Chromosomal DNA transfer can occur when the F-plasmid in an F+
cell integrates into the chromosome via homologous recombination.
Cells in which this has occurred are termed Hfr cells.

Front 126

Chromosomal DNA transfer can occur when the F-plasmid in an F+
cell integrates into the chromosome via __________.

Back 126

homologous recombination.

Front 127

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

Back 127

?

Front 128

Info card

Chromosomal DNA transfer can occur when the F-plasmid in an F+
cell integrates into the chromosome via homologous recombination.
Cells in which this has occurred are termed Hfr cells. Chromosomal
DNA can now be transferred via a mechanism very similar to plasmid
transfer, however the two cells (donor and recipient) break contact
before the entire chromosome can be transferred. The interesting part
about this is that the F-plasmid itself is one of the last things on the
chromosome so it is not transferred to the recipient cell, thus recipient
cells remain F-.

Back 128

i

Front 129

Practice: 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.

Back 129

d. all the above

Front 130

Info card:

An antibiotic is technically defined as an antimicrobial drug produced
naturally by a microorganism. However, the term is used slightly loosely as
many drugs are partially synthetic (e.g. ampicillin) or synthetic (e.g. sulfa
drugs) and are still termed antibiotics.

Back 130

i

Front 131

therapeutic index, how to
calculate it and what it means.

Back 131

Quantitatively, it is the ratio given by the lethal or toxic dose divided by the therapeutic dose.


http://en.wikipedia.org/wiki/Therapeutic_index

Front 132

Which drug inhibits cell wall synthesis?

Back 132

The beta-lactam drugs

Front 133

Practice: Beta-lactam drugs
a. are most commonly thought to inhibit the enzymes
responsible for forming the tetrapeptide chains between
strands 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

Back 133

g,. all of the above

Front 134

Practice: The broad-spectrum penicillins
a. are effective against both Gram-positive and Gramnegative
organisms.
b. are isolated directly from Penicillium chrysogenum and
undergo no further modification.
c. include penicillin G and Penicillin V.
d. include ampicillin and amoxicillin.
e. a and d
f. b and c

Back 134

e. a and d

Front 135

Practice: The extended-spectrum penicillins
a. are partially synthetic.
b. are the cephalosporins.
c. include cephalexin.
d. are effective against some tough Gram-negative bacteria
like Pseudomonas.
e. a and d
f. b and c

Back 135

e. a and d

Front 136

List 3 purposed of Vancomycin

Back 136

Vancomycin
a. Stops peptidoglycan synthesis by binding to the NAM side
chains and precluding the linkage of the peptidoglycan layers.
b. Often used when the beta-lactam antibiotics are ineffective but
it must be administered intravenously.
c. Can’t cross the outer membrane of Gram-negatives and is
thus ineffective against these organisms.

Front 137

Practice: Bacitracin
a. inhibits cell wall synthesis by interfering with the
transport of peptidoglycan precursors across the
cytoplasmic membranes.
b. is administered intravenously.
c. is used only in topical ointments.
d. a and b
e. a and c

Back 137

e. a and c

Front 138

List 3 drugs the inhibit protein synthesis

Back 138

a. tetracycline
b. streptomycin
d. erythromycin

Front 139

Practice: Which one of the following is a drug that DOES NOT
inhibit protein synthesis?
a. tetracycline
b. streptomycin
c. cephalexin
d. erythromycin

Back 139

c. cephalexin

Front 140

Practice: The tetracyclines
a. bind to the 30S ribosomal subunit causing it to distort
and malfunction.
b. include gentamicin and neomycin.
c. include doxycycline.
d. both a and b

Back 140

c. include doxycycline

Front 141

Practice: Erythromycin is an aminoglycoside (T or F).

Back 141

False.

Front 142

Which class of drugs that inhibit nucleic acid
synthesis?

Example?

Back 142

These are the fluoroquinolones and they inhibit the
topoisomerases

Cprofloxacin is an example.

Front 143

Polymyxin B targets the cell how?

How is it applied?

Back 143

Polymyxin B perturbs cell membranes and is used only topically

Front 144

Antiviral and antifungal drugs - Speculate as to why they are more difficult
to develop?

Back 144

Fungi - eukaroytic
viruses - integrate into cell dna.