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Microbiology > Unit 7 Microbial Genetics > Flashcards

Unit 7 Microbial Genetics Flashcards

1
Q

Bacterial genome

A

Total collection of genes carried by a bacterium:
- chromosome
- extra chromosomal material like plasmids or bacteriophages

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2
Q

Gene

A

Sequence of nucleotides that has a biological function

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3
Q

Phenotype

A

Morphological or physiological manifestation of the genotype

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4
Q

By what is the phenotype determined

A

By the interaction of the expression of the genome and the external influence of the environment

NOT every character is encoded genetically

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5
Q

Genotype

A

Specific set of gens of an organism
Inherited
Not all genes are expressed phenotypically

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6
Q

Phenotypic variations properties

A
  • High frequency, affecting the entire population exposed to the environmental pressure
  • Reversible, returning to the original state when the generating cause disappears
  • Not inherited, no change in the DNA
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7
Q

Types of phenotypic variations

A

Morphological : apparition of mucus layer in media with sucrose

Chromogenic : color changes depending on temperature

Enzymatic : capacity to produce enzymes only in the presence of the substrate. E g production of penicillinase in the presence of penicillin

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8
Q

Mutation definition
Causes

A

Persistant change of DNA bases without addition of exogenous DNA

Arise
-spontaneously,
-because of mutagens or
-transposable elements

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9
Q

Random facts bacterial mutations

A

-High speed duplication

-DNA repair system of bacteria
produces higher frequency of errors than any species

-Lots of mutations are incompatible with life
-Some spécificité mutation can provide thé mutant BIOLOGICAL ADVANTAGE

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10
Q

Characteristics of mutation

A

-Low frequency : but can be increased by mutagen agent
- Irreversible
- Inherited
- Spécificité: Affects specific character
- spontaneous mutation

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11
Q

Selector agent

A

Selects a spontaneous mutation by killing the specimens that aren’t resistant to it

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12
Q

Exemple of mutations in bacteria

A
  • Alteration of surface components such as capsule or flagella
  • Loss of ability to synthesize growth factor( auxotroph)
    -Resistance to antibiotics
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13
Q

Types of mutations

A

Substitution
Deletion
Insertion

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14
Q

How is a mutation called when it affects a single base

A

Point mutation

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15
Q

After the translation it can result in three types of mutations

A
  • Non sens ( no protein/ terminal codon )
    -Missense ( altered protein)
  • Silent
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16
Q

Non sense mutation

A

Premature terminal codon
No protein

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17
Q

Missense

A

Altered protein

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18
Q

Silent mutation

A

Same protein

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19
Q

Frameshift mutations

A

Insertion or deletion of number of nucleotides that is not a multiple of 3

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20
Q

Spontaneous mutation

A

Random errors in replication

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21
Q

Induced mutations
Why
Types

A

From exposure to known mutagens
- Physical agents : ionizing, UV
- Chemical agents ( substitution or insertion )

22
Q

Chemical agents that cause mutations

A

Substitutions:
- Nitrous acid ( transforms adenine in hypoxanthine that binds to cytosine)
- 5-bromouracil (replaces thymine and binds to guanine)

Insertion : Acridine orange that is an intercalant agent

23
Q

Transposable elements/transposons

A

Segment of DNA that has the capacity to “jump” to different locations in the genome. Produce insertions and deletions

24
Q

Transposable elements/Transposon are made of

A

IR inverted repeat

Transposases, enzymes that cut the DNA

25
Q

Inverted repeat

A

Small nucleotide sequence located at the ends of the transposon. Inverted

26
Q

Where do transposases cut

A

( DR )direct repeats
Few nucleotides on both ends, not inverted

27
Q

Types of Transposable elements

A

Insertion sequences
Complex Transposon
Other

28
Q

DNA repair system made of

A

Specific enzymes
Excision repair system
Recombination system
SOS repair system

29
Q

What’s a reversion

A

Reverse mutation returns to the wild type genotype

30
Q

Exemple specific enzyme repair system

A

Photolyase corrects the damage done by UV radiation

31
Q

Excision repair system

A

Damage chain gets cut by endonuclease and re-synthesized by polymerase and ligase

32
Q

Recombination system

A

Damaged chain gets cut, replace by the homologous fragment that is then resynthesized

33
Q

SOS repair system

A

System of enzymes that repairs severely damaged DNA

34
Q

Genetic transfer

A

Entry of foreign DNA within the bacteria from the surroundings

3 types
Environment : Transformation
Another bacteria : Conjugation
Bacteriophage : Transduction

35
Q

Exogenous DNA can react in three ways

A

Degradation
Circulation
Recombination

36
Q

Degradation

A

The new DNA is destroyed by endonucleases that recognize it as foreign

37
Q

Circulation

A

Methylated to avoid the action of endonucleases

Then it can replicate independently of bacterial DNA (transmitted to daughter cells)
Or don’t replicate and will be lost in successive divisions (abortive process)

Plasmid can be both

38
Q

Endonucleases

A

Enzyme that destroys foreign DNA

39
Q

Recombination

A

Genetic exchange between bacterial DNA and exogenous DNA
➡️ Mixed genetic information

40
Q

Transformation

A

The uptake by a cell of a naked DNA molecule of the medium and it’s incorporation into the recipient chromosome in a heritable form

Happens after cell lysis, that releases its compounds in the environment

41
Q

Transformation usually occurs between cells that share the same

A

Ecological niche
E g 2 bacteria in colon

42
Q

Bacteria able to take up the DNA from environment

A

Competent bacteria

43
Q

How to artificially induce transformation

A

Electrical shock or calcium chloride

44
Q

Conjugation

A

Transfer of genetic material between two bacteria by direct contact between them

Different for gram + or -

45
Q

Conjugation gram-

A

Transfer of plasmid via sex pilus
After the conjugation, the receptor f- can become f+

46
Q

Transduction

A

Induced by bacteriophages, that inject the viral DNA

Virulent phages
Attenuated phages

47
Q

Virulent phages

A

Use the enzymatic machinery to synthesize bacterial phage structures.
They create viral progeny breaking the bacteria to get out
Lytic cycle

48
Q

Attenuated phages

A

DNA of the phage is integrated into the cell genome and doesn’t produce lysis
Lysogenic cycle

49
Q

Lytic cycle

A

Results in the destruction of the infected cell

50
Q

Insertion or deletion of a number of nucleotides that’s not a multiple of 3

A

Frameshift mutation

51
Q

Name cycle attenuated phages

A

Lysogenic cycle

52
Q

When the bacteria is killed because of bacteriophage

A

Lytic cycle

Microbiology (12 decks)

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