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Microbio Exam 1 > microbial genetics 3 > Flashcards

microbial genetics 3 Flashcards

1
Q

Bacterial chromosome

A

Single, large circular DNA molecule

~1-6 megabases

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2
Q

Plasmid

A

Small, circular DNA molecule

Separate from bacterial chromosome, but replicated and transferred to daughter cells

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3
Q

Bacterial genome characteristics

A

Small
1 chromosome

Haploid

No exons/introns/histones

Transcription/translation are coupled

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4
Q

Polycistronic mRNA

A

An mRNA molecule that contains information from multiple genes by a single promoter

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5
Q

Bacterial gene repression

A

A repressor binds to the operator of the gene, and transcription will not occur
Regulators can bind to the repressor, removing it and allowing transcription

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6
Q

Bacterial positive gene regulation

A

Low affinity RNA polymerase may require an activator binding to the gene before the polymerase can bind

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7
Q

Bacterial vertical gene transfer

A

Genes are passed to progeny of bacteria

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8
Q

Bacterial horizontal gene transfer

A

Genes are passed from one bacteria to another bacteria

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9
Q

Methods of bacterial horizontal gene transfer

A

Transformation
Conjugation

Transduction

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10
Q

Evolution of bacteria

A

Unassisted, bacteria would adapt incredibly slowly

DNA repair is good

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11
Q

How is bacterial evolution enhanced?

A

The development of horizontal gene transfer

New virulence factors can be developed through this process

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12
Q

Homologous recombination

A

Exchange of DNA between two DNA molecules based on homology

Mediated by RecA

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13
Q

Transformation

A

Uptake of free DNA from environment

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14
Q

Process of transformation

A

DNA is released into environment (bacterial death) - this DNA is not protected
DNA is actively imported into bacterial cells

Homologous recombination

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15
Q

Conjugation

A

DNA transfer directly from one bacterial cell to another via cell contact

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16
Q

Process of conjugation

A 
Fertility factor (F-Factor)
Sex pilus formation

DNA transferred from donor to recipient bacterium - homologous recombination

17
Q

F-Factor

A

Carries genes, tra operon, and oriT

18
Q

Tra operon

A

Encodes the sex pilus

19
Q

Sex pilus

A

Bridge that allows the transfer of genetic information from one cell to another

20
Q

OriT

A

Origin of transfer

Where a single strand break occurs for transfer

21
Q

Recipient bacterium

A

Must be F- (no F-Factor) or cannot receive information from sex pilus

22
Q

F+ x F- conjugation

A

F- -> F+
Only a single strand is transferred, no bacterial genes are transferred

NO homologous recombination

23
Q

Hfr x F- conjugation

A

Bacterial genes transferred from Hfr to F-
Process begins at OriT, tra operon is the last thing transferred

Homologous recombination

24
Q

Generalized transduction

A

A lytic bacteriophage incorporates bacterial chromosome into its phage head
When the phage infects another bacteria, DNA can be incorporated via homologous recombination

25
Q

Specialized transduction

A 
Lysogenic phage incorporates into the chromosome as a prophage
Some event (UV damage) leads to conversion to a lytic lifecycle

Small portion of the chromosome is packaged into phage head after excision from the genome (only genes adjacent to phage insertion are transferred)

26
Q

Three general categories of antibiotic resistance

A

Intrinsic
Chromosome-mediated

Plasmid-mediated

27
Q

Intrinsic antibiotic resistance

A

Unable to be horizontally transferred
Not increasing among bacterial populations

i.e. lack of an antibiotic target (lack of peptidoglycan)

28
Q

Chromosome-mediated antibiotic resistance

A

Genes encode antibiotic resistance
Arises via random mutation or horizontal gene transfer

i.e. penicillin-binding proteins, DNA gyrase, etc.

29
Q

Plasmid-mediated antibiotic resistance

A

Genes on plasmid encode antibiotic resistance

Usually degrade or modify antibiotic, or pump it out of cell

30
Q

Resistance factor

A

Has a resistance transfer factor and a resistance determinant

31
Q

Resistance transfer factor

A

Equivalent to F-factor because it encodes everything needed for conjugation

32
Q

Resistance determinant

A

Gene(s) for drug resistance

33
Q

Transposons

A

Mobile DNA elements that can move from one molecule of DNA to another
Palindromic sequences

34
Q

TnpA

A

Enzyme (transposase) required for transposon movement

35
Q

Integrons

A

Can capture antibiotic resistance cassettes and integrate them into the bacterial DNA
Often associated with large mobile genetic elements, like transposons

36
Q

Pathogenicity islands

A

Region of bacterial chromosome acquired through horizontal gene transfer
Often carry coordinately regulated virulence genes surrounded by insertion sequences

Microbio Exam 1 (8 decks)

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