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70 Cards in this Set

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  • Back
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What is the control mechanism for the LAC operon? x2

What is the control mechanism for the Trp operon? x2

Define mutation
Heritable changes in the nucleotide sequence
T/F - Mutations usually give rise to phenotypic changes.
False. They usually don't always give rise to phenotypic changes, but can lead to disease.
Define tautomerization
An inserted base
will change its
base pairing
Mutagens increase the rate of what?
Most carcinogens are mutagenic, but......
not all mutagens are carcinogens
Define silent mutation.

Occurs often where?
DNA mutation without change in amino acid

often at the 3'position of codon
(tRNA wobble)
Define Missense mutation
Base change or substitution alters the type of amino acid
MIStake amino acid
Define Nonsense mutation
Base change causes sequence changes, such that the chain terminates
NOnsense = NO more elongation
Define Frameshift mutation
Insertion or deletion of bases (not divisible by 3) that changes the reading frame.
Define Null mutation
Insertion or deletion of large chunks of DNA.
Define Direct DNA repair.
Direct enzymatic repair of dimers.
Define Excision repair
Excision of DNA segment containing damaged DNA followed up by synthesis of new strand
Define SOS response
Forced induction of many genes after DNA damage, bypassing the errors of DNA
Define error-prone repair
Last resort before death
Transfer of DNA occurs through the form of what Components? x3

- what are they
- how do they replicate
- can they integrate into chromosomes?
Circular INDEPENDENT pieces of dsDNA

Replicate AUTONOMOUSLY via origin of replication

What encodes the conjugation apparatus including the sex pili and tra genes?
What are the two main groups of plasmids and describe?
Large plasmids that are self transmissable
(b/c can form Conjugative Apparatus)

Small plasmids that are NON-conjugative
(can NOT form conjugative apparatus, but may follow its route)
What codes for bacterial toxins?
What codes for Antibiotic resistance?
What are the two parts of the R Plasmids?
Resistant Transfer Factor (RTF)

R Determinant
What does the RTF & R Determinant code for?
Encodes resistance to antibiotics
What forms when the F plasmid integrates into the bacterial chromosome?
HFr Strain
What happens to R plasmids when selection pressure is lessened?
It is unstable to begin with, so it will become lost.
T/F - Phages can replicate outside living cells.
False, it cannot replicate outside living cells.
What does the One Step Growth curve measure? x2

Latency Period
Burst Size

of specific virus
What two cycles are possible when a Bacteriophage infects a cell?
Lytic cycle

Lysogenic cycle
Define prophage
A phage genome inserted as part of the DNA chromosome of a bacterium.
Define lysogen
Bacterium in the state of a lysogenic cycle
List the mechanisms for gene transfer. x3


Explain transformation
Gene transfer between bacteria by means of "naked" DNA fragments, thus transforming the receiving bacteria's DNA
Give a basic definition of Transduction.
Transfer of viral, bacterial, or both bacterial and viral DNA from one cell to another VIA Bacteriophage
What are the two types of transduction?

Bacteriophage gene regulation is tightly regulated in what kind of fashion?
In a temporal fashion.
Generalized Transduction:

- Occurs during which cycle
- What happens
There you go bizzzzaaattttcccchhhh!!!!
Specialized Transduction:

- occurs during what cycle
- what happens
What is the most frequent form of gene transfer?

- occurs between?
- requires presence of what? x2
CAN be between differing bacterial species.

Sex pili & Cell to cell contact
List two types of Mobile DNA elements in Bacteria
1. Bacterial Insertion Sequences (IS)

2. Bacterial Transposons
Bacterial Insertion Sequences (IS):

- what are they
- mechanism of movment
50-bp inverted repeats flanking regions encoding transposase.
(+/- resolvase)

Excision/copying of DNA and its insertion at the target site.
Bacterial Transposons:

- what are they
- mechanism of movement
Central antibiotic resistance gene flanked by IS elements

Copying of DNA and its insertion at target site
The Ara Operon utilizes what control mechanism?
Positive control of induction
Describe the Negative control of induction associated with the Lac Operon.
With NO lactose, the operon is OFF

Repressor BOUND (thus neg. control)

With ADDED lactose, it binds to repressor, changing its conformation. Thus releasing itself.
Describe the Positive control of induction associated with the Lac Operon.
With ADDED lactose,

cAMP generated

cAMP binds with CAP

Binds to promoter region, thus enhancing transcription
Describe the Negative control of Repression associated with the Trp Operon.
No Trp means No Repressor bound

With ADDED Trp, it binds to inactive repressor

Thus activating repressor which binds operon.
Describe the process of attenuation associated with the Trp Operon when there is no Trp available
Polymerase stalls on sequence 1

Sequence 2 & 3 bind

Thus NO Termination

Enzymes transcribed
Describe the process of attenuation associated with the Trp Operon when there is Trp available
Ribosome terminates when it encounters the 2 Trp on the leader sequence.

Thus sequence 1 & 2 bind
Thus sequence 3 & 4 bind

Thus creating Rho independent Termination
(hairpin & Loop with Poly U stretch)
T/F - Plasmids can produce different sex pili.
T/F - Plasmids can not be in the same incompatible group.

Plasmids CAN be in the Same Incompatible group
What can be used for cloning specific DNA fragments?
Plasmids can code for what? x3
1. Bacterial Toxins

2. Enzymes that metabolize unusual substrates

3. Antibiotic resistance (R plasmids)
Hfr-strain is formed when what happens?
F plasmid integrates into bacterial chromosome
Which infected cells are immune from Superinfections from the SAME phage?
Lysogenic cells
(with latent phage)
T/F - The genetic material of a phage is always DNA.

Can be DNA or RNA
In generalized transduction, what genes are involved?

what phage is involved?
Any bacterial gene
(is randomly taken and put into capsid)

Lytic phage
In specialized transduction, what genes are involved?

what phage is involved?
Restricted Phage genes
(specifically put between bacteria genes: lac & biotin)

Lysogenic phage
Conjugation requires? x2
1. Cell to cell contact

2. Sex pili
F-plasmids encode for what?
Conjugation apparatus

includes pili AND tra ("transfer") genes
T/F - Non-conjugative plasmids exist but can not be transferred along with conjugative plasmids.

Non-conjugative plasmids CAN be transferred along with conjugative plasmids.
Transformation can occur (tho rare) but requires what criteria?
Bacteria must be in state of COMPETENCE
T/F - Transformation works in human cells?
What type of gene transfer requires the presence of a phage?
In conjugation, what initiates the "rolling circle" replication? x2
1. Single stranded nick @ OriT

2. Binding of protein @ 5' end
R-plasmids can be ACQUIRED how?

R-plasmids can be TRANSFERRED how?

What are the classes of Mutagens? x2
- Agents that Intercalcate
- Base analogs
- Chemicals that act like agents of alkylation

- Radiation
Give an example of a Physical Mutagen and the resulting effects.
UV light is a Physical Mutagen

causes Thymine Dimers to form
Define Recombination (or Post-Replication) Repair.
Retrieval of Missing Info
BOTH strands are damaged
Recombination (or PostReplication) repair:

- occurs when?
- does involve what process
- does NOT involve what process
- seen in what organism?
Both strands are damaged

Genetic Recombination

DNA Synthesis
(b/c template is damaged too)

(just swapping DNA around)