Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Bacteriology > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

Transformation

A

-process of importing DNA from the environment into bacterial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

competence

A
  • ability it take up new DNA

- done by perturbing the membrane by chemical (CaCl2) or electrical (electroporation) methods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Transformation in some Gram-positive species

A

-use a transformasometo become competent and acquire DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Transformation in some Gram-negative species

A
  • don’t use competence factors (CF).

- Either they are always competent, or they become competent when starved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Conjugation

A
  • transfer of DNA from one bacterium to another via cell-to-cell contact.
  • Often called “bacterial sex.”
  • initiated by a special sex pilus protruding from the donor cell
  • requires the presence of special (conjugal) plasmids-contain the genes needed for pilus formation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

fertility factor (F factor) plasmid

A
  • well-studied example of conjugal plasmid in E. coli
  • Contains two replication origins:
    1. oriV: used for normal replication
    2. oriT: used during DNA transfer

-begins with contact between the donor cell, called the F+ cell, and a recipient F– cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

conjugation process

A
  1. The sex pilus draws cells together
  2. The plasmid is nicked at oriT
  3. Rolling circle replication in donor cell
  4. Transferred ssDNA is replicated in recipient cell
  5. F- recipient cell is converted to F+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Agrobacterium tumefaciens

A
  • bacteria that can transfer genes across phylogenetic domains
  • causes crown gall disease
  • Contains a tumor-inducing plasmid (Ti) that can be transferred via conjugation to plant cells
  • transferred T-DNA “engineers” plant cells to proliferate and feed the Agrobacterium cells in the plant gall (tumor)
  • Can be used to transfer cloned genes into plant genomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Transduction

A
  • process in which bacteriophages carry host DNA from one cell to another
  • occurs accidentally as an offshoot of the phage life cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Generalized transduction

A

-can transfer any gene from a donor to a recipient cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

protection system, restriction and modification, involves

A
  • Enzymatic cleavage of alien DNA, by restriction endonucleases that recognize specific short sequences
  • Protective methylation of those sequences in the host’s own DNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Generalized recombination

A

requires a considerable stretch of homologous DNA sequences, which are very similar in sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Site-specific recombination

A
  • requires short specific sequences that are the same between the recombining DNA molecules.
  • specific short sequences are recognized by specific recombination enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

RecA protein

A
  • required by Generalized recombination
  • molecules are also called synaptases
  • They scan DNA molecules for homology and align the homologous regions, forming a triplex DNA molecule, or synapse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

site-specific recombinase enzyme

A

-involves very short specific homology sequences between donor and target DNA molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Point mutation

A

change in a single base

17
Q

Insertion and deletion

A

addition or subtraction of one or more bases

18
Q

Inversion

A
  • DNA segment is flipped in orientation

- Mutations are reversible

19
Q

Reversion

A

DNA mutates back to original sequence

20
Q

Silent mutation

A

does not change the amino acid sequence

21
Q

Missense mutation

A

-changes an amino acid

22
Q

Nonsense mutation

A

-changes a codon to a stop codon

23
Q

Frame-shift mutation

A

changes the reading frame of the ORF so that all following codons are all wrong

24
Q

mutations arise naturally for 2 reasons

A
  1. Chemical shifts in DNA bases that alter base-pairing properties
  2. Oxidative deamination of bases and formation of apurinic sites
25
Q

Chemical mutagens

A
  • Base analogs
  • Base modifiers: alkylating and deaminating agents
  • Chemical intercalators that bind to and distort DNA
26
Q

Electromagnetic radiation as mutagens

A
  • X-rays and gamma rays: break the DNA

- Ultraviolet rays (from sunlight): form pyrimidine dimers

27
Q

Ames test

A
  • relies on a mutant bacterial strain that is defective in the hisG gene
  • Cannot grow on a medium lacking histidine
  • mutagen-containing disk is placed on an agar plate with a thin lawn of the mutant strain
  • mutagen causes reversion mutations, and colonies start to appear around the disk
28
Q

Error-proof repair pathways

A
  • which prevent mutations
  • Methyl mismatch repair
  • Photoreactivation
  • Nucleotide excision repair
  • Base excision repair
  • Recombinational repair
29
Q

Error-prone repair pathways

A
  • which risk introducing mutations

- Operate only when damage is so severe that the cell has no other choice but to die

30
Q

Error-Prone DNA Repair -SOS (“Save Our Ship”) repair

A
  • Induced by extensive DNA damage
  • causes increase in ssDNA
  • causes expression of many DNA repair enzymes
  • two “sloppy” DNA polymerases that lack proofreading activity
  • cell has no other option but to “mutate or die”
31
Q

Nucleotide excision repair

A
  • Thymine dimer
  • DNA is cut
  • DNA Polymerase and DNA ligase repair the damage
32
Q

Transposable elements

A
  • move from one position in DNA to another
  • Exist in virtually all life-forms
  • Can move within and between chromosomes
33
Q

Insertion sequence (IS)

A
  • Simple transposable elements containing a transposase gene, flanked by short inverted repeat sequences
  • are targets for the transposase enzyme

two mechanisms:

  1. Nonreplicative (cut and paste)
  2. Replicative transposition
34
Q

Transposons

A

carry additional genes

35
Q

Horizontal Gene Transfer

A

-Sometimes multiple genes are acquired
-Genomic islands move by horizontal gene transfer
-DNA region that contains many genes
-Provide acquisition of new complex phenotypes including:
Pathogenicity islands
Symbiosis islands
Fitness islands

36
Q

Genome reduction

A
  • the loss of genes through evolution
  • Genes no longer needed in ecological niche
  • Over half of the Mycobacterium leprae genome is composed of nonfunctional pseudogenes, which are not expressed
37
Q

Duplications and Divergence

A
  • Duplication frees a gene from its previous functional constraints and allows divergent evolution through mutation.
  • Families of related proteins arise by divergent evolution and share structural and functional features, but may catalyze different reactions

Bacteriology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions