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Block 6 Week 3 > Kozel: Bacterial Genetics > Flashcards

Kozel: Bacterial Genetics Flashcards

1
Q

What is this:

Under control of promoter or repressor DNA sequence; can activate or turn off expression of a gene or group of genes.

A

operon

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2
Q

This is the most common form of control of gene expression in bacteria

A

negative regulation

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3
Q

How many genes are involved in lactose degradation? What are they?

A

3; promotor region which initiates transcription, the operon which allows for transcription, and the regulatory gene which codes for the repressor protein

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4
Q

Explain how the lactose operon is an example of negative regulation.

A

In the absence of lactose, the operon is bound by the repressor protein and cannot transcribe genes involved in lactose metabolism. When lactose is present, lactose binds to the repressor protein and turns it OFF so that transcription can occur

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5
Q

So, when lactose is not present, the repressor is (blank) and the operon is (blank). As a result, gene transcription is (blank)

A

active; off; prevented

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6
Q

When lactose is present, the repressor is (blank) and the operon is (blank). As a result, gene transcription (blank)

A

inactive; on; is active

**lactose –> inactive repressor –> active operon –> transcription

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7
Q

Are mutations in bacterial genome an efficient means for development of antibiotic resistance?

A

no

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8
Q

What is this:

the uptake of naked DNA

A

transformation

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9
Q

What is this:

one-way direct cell-to-cell transfer of DNA through a sex pilus

A

conjugation

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10
Q

What is this:

transfer via bacterial viruses, usually between the same or closely related species

A

transduction

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11
Q

Which method of genetic exchange is a common means for transfer of Ab resistance BETWEEN species

A

conjugation

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12
Q

What are the two flavors of transduction?

A

generalized

specialized

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13
Q

What type of transduction is this:

random due to accidental packaging of host DNA into phage

A

generalized

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14
Q

What type of transduction is this:

genes adjacent to sites for integration of phage DNA into bacterial genome

A

specialized

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15
Q

Describe the experiment in which transformation, or uptake of naked DNA, was first demonstrated.

A

Mouse injected with living encapsulated bacteria died.
Mouse injected with living non-encapsulated bacteria lived.
Mouse injected with heat-killed encapsulated bacteria lived.
Mouse injected with both heat-killed encapsulated bacteria and non-encapsulated bacteria died! (the DNA was transferred from the dead encapsulated bacteria)

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16
Q

Only certain species can undergo transformation. Name two.

A

Streptococcus pneumoniae

Neisseria gonorrhea

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17
Q

In transformation, how is DNA integrated into a new chromosome?

A

by homologous recombination

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18
Q

What is this:

one way transfer of DNA from a donor (male) cell to a recipient (female) though a sex pilus
Requires direct cell contact

A

conjugation

19
Q

What special factor is required in the donor cell for conjugation? How is this factor maintained?

A

F factor (fertility factor); maintained as a plasmid

20
Q

small genetic elements that can replicate independently of the bacterial chromosome

A

plasmid

21
Q

a plasmid that can integrate into the host chromosome

A

episome

22
Q

How is the F factor transferred from donor cell to host cell?

A

the F factor transfers itself from host to recipient

there is an F plasmid which carries all of the genes necessary for its own transfer ex: ability to make the sex pilus

there is an F pilus that brings the recipient cell in close proximity with the host cell so that the F factor can be transferred

23
Q

What happens once the F factor is transferred from donor to host?

A

The F factor can be inserted into the host chromosome. It makes the cell F+. It also makes the cell a high frequency of recombination cell.

24
Q

What does a host cell become once it receives Factor F from a donor cell?

A

high frequency of combination cell

**recombination can occur between the Hfr chromosome fragment and the original host chromosome

25
Q

Why are plasmids useful to bacteria?

A

they carry genes for resistance to many antibiotics and antibacterial compounds; they also carry genes for virulence and toxicity

26
Q

What is this?

transfer of DNA within a cell, from one position to another in a genome (ex: from plasmid to genome)

A

transposons

27
Q

What is a simple transposon?

A

A simple transposon uses transposase to recognize inverted repeats in the DNA. It will then disconnect a sequence from the DNA and insert that sequence into a new DNA site

28
Q

How is DNA rearrangement via simple transposons different from homologous recombination?

A

unlike homologous recombination, transposons do not require a homologous chromosome at their site of insertion

29
Q

How are complex transposons different from simple transposons?

A

complex transposons not only transfer DNA from one site to another, but they also carry/insert additional genes, such as genes that convey antibiotic resistance or toxin production

30
Q

What are conjugal resistance plasmids? What do they contain?

A

They contain a resistance transfer factor (which encodes genes needed for transfer via conjugation) and they carry drug-resistant transposons

**very dangerous, because if they contain multiple resistance genes, they can allow for bacteria to become resistance to multiple antibiotics at once

31
Q

What is this:

the process by which DNA is transferred from one bacterium to another by a virus (bacteriophage)

A

transduction

32
Q

What is this:

the process by which any bacterial gene may be transferred to another bacterium via a bacteriophage, and typically carries only bacterial DNA and no viral DNA

**due to accidental packaging of the host DNA

A

generalized transduction

33
Q

What is this:

the process by which a restricted set of bacterial genes (from the phage genome) is transferred to another bacterium. The genes that get transferred depend on where the phage genome is located on the chromosome

A

specialized transduction

34
Q

Describe the bacteriophage life cycle

A
  1. Phage attaches to a bacteria host cell and injects DNA
  2. Phage DNA becomes circular and either enters lytic or lysogenic cycle
  3. In the lytic cycle the new phage DNA will be assembled into virions, the cell lyses, and the phage virions are released
  4. In the lysogenic cycle, phage DNA will integrate into the bacterial chromosome and form a prophage. This new recombinant DNA will reproduce generating several copies
35
Q

So explain the difference between the lytic and lysogenic cycle of bacteria

A

lytic:

  1. virus attaches to host bacteria cell via bacteriophage
  2. viral DNA is injected into host cell
  3. virus takes over host cell’s machinery and makes several copies of the phage until the cell lyses and releases TONS of bacteriophages with viral DNA

lysogenic (no pathology):

  1. virus attaches to the host bacteria cell via bacteriophage
  2. viral DNA is injected into the host cell
  3. the viral DNA recombines with the bacterial host cell DNA (prophage)
  4. the cell with the mixed bacterial/viral DNA will divide and produce several copies
36
Q

Give an example of generalized transduction

A

A bacteriophage attaches to a donor bacterial cell and infects it with viral DNA. Viral DNA is replicated, while the bacterial DNA is broken down into pieces. Pieces of phage DNA and bacterial DNA form separate phage capsids. The cell lyses and phage capsids are released. A phage with bacterial DNA from the initial infected cell can then go on to infect a new host cell and produce a new recombinant DNA.

37
Q

Give an example of specialized transduction.

A

A prophage (bacterial + viral DNA) exists in a galactose-using host cell. The viral (phage) portion of the DNA is excised and takes with it an adjacent bacterial gene from the host (this gene confers the ability to break down galactose). The cell lyses and this new phage with the galactose gene from the host infects a new cell that cannot utilize galactose. The phage + bacterial galactose gene are inserted into newly infected cell’s DNA and the new cell can now metabolize galactose.

38
Q

What is the most common means by which bacterial cells control gene expression?

A

transcription control

**repressor proteins that block trx

39
Q

What is this:

transfer of DNA from a donor to a recipient via a BACTERIOPHAGE

via cell-to-cell contact

via naked DNA in solution

A

transduction; conjugation; transformation

40
Q

Finally, compare transduction to transformation to conjugation.

A

transduction is the transfer of DNA from a host to a recipient via a bacteriophage; transformation is the transfer of DNA from a host to a recipient via naked DNA transfer; conjugation is transfer using cell-to-cell contact and the transfer of the F factor via the sex pilus

41
Q

Which type of DNA transfer is susceptible to DNA breakdown during transfer by DNase?

A

transformation (free DNA)

42
Q

Requires both an insertion sequence and a transposase in additional to the bacterial DNA

A

transposons

43
Q

Transducing phage particles contain phage DNA linked to bacterial DNA

A

specialized transduction

44
Q

Transducing phage particles contain only bacterial DNA

A

generalized transduction

Block 6 Week 3 (6 decks)

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