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microbiology > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

What is a mutation?

A

Any heritable change or alteration of DNA

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2
Q

What is haploid?

A

Bacteria have a single copy of each gene in chromosome; therefore, mutation has potential for an immediate effect on phenotype of the bacterium

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3
Q

How can alterations in DNA occur?

A
  • naturally

* via an external process (irradiation)

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4
Q

At what rate does spontaneous or random mutagenesis?

A
  • occurs at a constant rate

* 1 in 10^6 to 10^8 per generation

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5
Q

How does bacterial division occur?

A
  • A bacteria will duplicate its chromosome
  • The cell continues to grow and starts to pinch in the middle
  • The cell divides into two cells with one copy of chromosome each
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6
Q

One single chromosome can encode up to how many genes?

A

3,000

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7
Q

Do bacteria have histones? If not, what do they have?

A
  • No, they don’t have histones

* They carry their own replication enzymes (DNA and RNA polymerases)

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8
Q

When must chromosomes divide?

A

They must divide when the cell divides.

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9
Q

What are point mutations? What are the different effects they can have?

A
  • Point mutations are single base pair mutations

* Varied effects depending on the resulting codon

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10
Q

What is a missense mutation?

A
  • Mutation changes a polypeptide to inactive or non-functional.
  • code for a different amino acid
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11
Q

What is a silent mutation?

A
  • some have little or no implication to the phenotype

* they code for the same amino acid

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12
Q

What is a non-sense mutation?

A

Inserts a stop codon in place of the expected residue and can result in dramatic changes in phenotype

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13
Q

Spontaneous mutations can result from what?

A

From imperfect replication of DNA or insertion of moveable genetic elements called transposons.

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14
Q

What does a transposon recognize?

A

It recognizes a very small site, usually less than 10 nucleotides.

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15
Q

Bacterial transpositions medically relevant in what 3 ways?

A
  • often carry antibiotic resistance
  • move between species and genera
  • cause mutation if inserted into gene
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16
Q

What is transposition?

A

It is a site specific recombination using a recombinase called a transposes. You can have a piece of DNA insertion, or a piece of circular DNA insert to get site specific recombination.

17
Q

What does tranposase allow?

A

Entry into target cells

18
Q

What does resolvase do?

A

homologous recombination

19
Q

What is selection?

A

Drug resistance allows you to find the rare spontaneous mutation. It does not effect the rate at which it occurs. It can happen when someone doesn’t use their antibiotic correctly.

20
Q

What are the steps in genetic mutation causing drug resistance?

A
  • non-resistant bacteria exist
  • bacteria multiply by the billions
  • some mutations make the bacterium drug resistant
  • drug resistance bacteria multiply and thrive
21
Q

What are the steps in bacterial transformation?

A
  • donor bacterium
  • cell lysis
  • binding to recipient
  • DNA uptake
  • recombination
22
Q

What is lysis?

A

Strands of DNA are loose and bind to the bacterium and become part of the nucleoid region.

23
Q

What are plasmids?

A
  • transposons can be located in the extrachromosomal DNA
  • circular, supercoiled
  • one or more different plasmids per cell
  • one or more copies of the same plasmids per cell
24
Q

How are plasmids mobile?

A

They can be transferred between different bacteria species. Bacteria can obtain DNA from other bacteria.

25
Q

What do plasmids encode?

A

They encode antibiotic resistance genes (problem for multiple antibiotic resistance)
*also encode virulence factors (adhesions, toxins)

26
Q

What is bacterial conjugation?

A

Bacteria interact or adhere to surfaces and each other through filaments on the surface called pili (fimbrae).

27
Q

How can genetic material be transferred in bacteria?

A

By bacterial conjugation, but it must have direct contact to occur.

28
Q

How can you tell the gender of bacteria?

A
  • Male is F +, carries F plasmid, makes sex pilus

* Female is F -, no F plasmid, no sex pilus

29
Q

What is F in bacterial genetics/gender and sexduction?

A

F is fertility. Direct contact of an F + donor male with an F - recipient female via the sex pilus results in transfer or conjugation of the F plasmid.

30
Q

What is the net result of F (fertility)?

A

The net result is conversion of the F - female recipient to an F + male.

31
Q

What is required for conjugation to happen?

A
  • donor cell must have a F plasmid (compatible sex pilus)
  • requires direct contact between two bacterial cells via a pilus structure
  • DNA in the donor cell is transferred through the pilus and into the recipient cell
32
Q

What does bacterial transduction require?

A

viruses

33
Q

What is the process of phage infection?

A
  • virus makes contact
  • virus introduces its DNA into the bacteria
  • bacteria can use enzymes that digest foreign DNA not self DNA
34
Q

What is required for transduction to happen?

A
  • donor cell must carry a temperate bacteriophage (virus)
  • requires a specific lysogenic bacteriophage to transfer host genes from a donor bacterial strain to a recipient bacterial strain
  • new genes are integrated at the site of phage integration
35
Q

What are the steps of transduction?

A
  • donor is infected with phage
  • cell lysis by phage donor DNA in phage particle
  • injection of donor DNA into recipient cell (recombination)
  • recipient transductant with donor DNA
36
Q

Spontaneous mutations can result from imperfect replication of DNA or by the insertion of moveable genetic elements called ____?

A

Transposons

37
Q

What is the order for the selection of antimicrobial resistance?

A
  1. Non-resistant bacteria exist
  2. Bacteria multiply by billions
  3. Mutations make organisms drug resistant
  4. Drug resistant organisms multiply and thrive.
38
Q

What are some true statements about transduction?

A
  • transduction requires viruses
  • transduction requires a specific lysogenic bacteriophage
  • transduction mainly occurs via injection
  • does not occur with animal viruses

microbiology (10 decks)

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