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Microbio semester 2 > Bacterial Genetics > Flashcards

Bacterial Genetics Flashcards

1
Q

Give the definition for mutation

A

Heritable change in DNA sequence that can
lead to a change in phenotype

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2
Q

Give the definition for mutant

A

A strain of any cell or virus differing from
parental strain in genotype

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3
Q

What is a wild type strain?

A

It is a strain isolated from nature

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4
Q

What are the two types of mutation?

A

Selectable and non selectable

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5
Q

What is selectable mutations?

A

It gives the mutant a growth advantage in certain conditions (useful for genetic research)

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6
Q

What is non selectable mutations?

A

They dont give the parent advantages or disadvantages

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7
Q

What kind of methods are available for screening

A

Replica plating

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8
Q

What is replica plating useful for?

A

It is useful for the identification of cells with a nutritional requirement for growth

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9
Q

What are induced mutations?

A

They are made environmentally or deliberately
Can be results from exposure to radiation

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10
Q

What type of mutation can occur without
external intervention

A

Spontaneous mutation

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11
Q

What do point mutations change?

A

Theyre mutations that only change one bp

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12
Q

In point mutations, when the one Bp is changed, what can this lead to?

A

Can lead to single amino
acid change in a protein,
an incomplete protein, or
no change at all

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13
Q

What is the difference between a silent mutation and a missense mutation?

A

A silent mutation does not effect the amino acid sequence
A missense mutation, the amino acid changes and polypeptides are altered

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14
Q

What occurs with a nonsense mutation?

A

The codon becomes a stop codon and the polypeptide is incomplete

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15
Q

What can cause dramatic changes in DNA

A

Deletions and insertions

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16
Q

What do frameshift mutations do?

A

Deletions or insertions that result in a
shift in the reading frame

Which can often result in complete loss of gene function

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17
Q

What does genetic engineering allow for?

A

They allow the introduction of specific mutations
(site-directed
mutagenesis)

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18
Q

What type of mutation is typically reversable?

A

Point mutations

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19
Q

What is reversion

A

Its the Alteration in DNA that
reverses the effects of a prior
mutation

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20
Q

Revertant definition

A

Strain in which original phenotype is
restored

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21
Q

What are the two types of Revertant?

A

Same-site revertant: mutation is at
the same site as original mutation
Second-site revertant: mutation is at
a different site in the DNA

22
Q

Name the three ways to classify chemical mutagens

A

-Nucleotide base analogs: resemble nucleotides
-Chemical mutagens that
induce chemical modifications
-Chemical mutagens that
cause frameshift mutations

23
Q

Name the two types of mutagenic
electromagnetic radiation

A

Non ionizing (UV radiation)
Ionizing (X rays)

24
Q

What happens with non ionizing radiation?

A

Purines and pyrimidines strongly
absorb UV (pyrimidine dimer is an effect)

25
Q

What happens with ionizing radiation?

A

They Ionize water and produce free
radicals
Free radicals damage
macromolecules in the cell

26
Q

When DNA is damaged at a large scale, what type of repair system is used to fix it?

A

SOS regulatory system

27
Q

What does the SOS regulatory system do?

A

Allows replication to proceed and
cell to replicate, but errors are more likely

28
Q

Why is mutagenesis important?

A

If cells were perfect, there would be no evolution

29
Q

What test makes practical use of bacterial mutations to detect for potentially hazardous chemicals

A

The Ames test

30
Q

What does the Ames test look for?

A

Looks for an increase in mutation of
bacteria in the presence of suspected
mutagen

31
Q

Define Recombination

A

Physical exchange of DNA between genetic elements

32
Q

Define Homologous recombination

A

Process that results in genetic
exchange between homologous
DNA from two different sources

33
Q

What does transformation do?

A

The DNA is incorporated into a recipient cell and brings about genetic change

34
Q

What are plasmids?

A

Plasmids are circular pieces of DNA that exist outside the main bacterial chromosome and carry their own genes for specialised functions

35
Q

In genetic engineering, what do plasmids do?

A

They are used to introduce foreign genes into a bacterial cell

36
Q

What are plasmids who have the ampR gene resistant to?
What happens if plasmids dont have the gene?

A

the antibiotic ampicillin
Cells lacking the ampR plasmid are sensitive to the antibiotic, which kills them

37
Q

What does the LAC gene break down?

A

Lactose

38
Q

List the procedure for transformation

A

1) E.coli cells in log phase are moved into cold CaCl2 solution
2)ampR plasmids are added to the experimental cells
3) Cells are heat shocked at 42o
4) The treated cells are spread on an agar plate containing ampicillin
5)Incubated for 24 hrs
6)Only the colonies with ampR gene will grow

39
Q

What does electroporation entail?

A

Electricity is used to force cells to take up DNA

40
Q

What is Transfection?

A

Transformation of bacteria with DNA extracted from a bacterial virus

41
Q

What is transduction?

A

Transfer of DNA from one cell to another by a bacteriophage

42
Q

What are the two modes of transduction?

A

Generalised transduction
Specialised transduction

43
Q

Define generalised transduction

A

DNA from any portion of
the host genome is packaged inside the
virion

44
Q

Define specialised transduction

A

DNA from a specific
region of the host chromosome is
integrated directly into the virus genome

45
Q

In generalised transduction, what does the defective virus particle incorporate?

A

It incorporates fragment of the cell’s chromosome randomly

46
Q

In specialised transduction, what happens with the DNA of temperate virus

A

It excises incorrectly and
takes adjacent host genes
along with it

47
Q

Define Bacterial conjugation

A

mechanism of genetic transfer that
involves cell-to-cell contact

48
Q

List the essential features of bacterial conjugation

A

Plasmid-encoded mechanism
Donor cell: contains conjugative
plasmid
Recipient cell: does not contain plasmid

49
Q

Whats a fertility plasmid??

A

Circular DNA molecule
Contains genes that regulate DNA replication
Contains tra genes that encode
transfer functions

50
Q

What is a Sex pilus is essential
for?

A

Conjugation, its only produced by
donor cell

51
Q

How is DNA synthesised?

A

Rolling circle replication

52
Q

What are the two main types of
transposable elements in Bacteria?

A

transposons and insertion sequences

Microbio semester 2 (6 decks)

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