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Microbiology > Test 3 - Microbial Genetics > Flashcards

Test 3 - Microbial Genetics Flashcards

1
Q

Definition of Microbial Genetics (MG)

A

Interaction of ∆ genes within one organism or between organisms.

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2
Q

Reasons (4) to study MG. Practical examples?

A
  1. To gain basic understanding of gene function
  2. For biotechnology and cloning (e.g. GMO)
  3. For understanding virulence (e.g. harmful v. necessary E.coli)
  4. For understanding gene transfer (e.g. multi-drug resistance)
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3
Q

4 types of DNA transfer?

A
  1. Transformation
  2. Transduction
  3. Conjugation
  4. Sexual Mating
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4
Q

Transformation: What is Transformation?

A

Transfer of naked DNA directly from environment.

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5
Q

Transformation: Ability to pick up DNA to be transformed is __(a)__. This ability is pronounced when __(b)__.

A

(a) Competency

(b) under stressful situations such as overcrowding.

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6
Q

Transformation: Take overcrowding as an example situation in which competency is pronounced. How does the cell know that it is overcrowded in the first place?

A

Concentration of quorum sensing factor, or [CF]. +cells –> +[CF]

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7
Q

Transformation: Relate CF, Cam D, Cam E, cam X, and Sig H. What are their functions?

A

When [CF] is sufficiently high, Cam D (a CF receptor) binds to CF. CF-CamD phosphorylates Cam E. Cam E causes transcription and translation of gene cam X, which codes for Sig H. Sig H activates genes for proteins required for bringing the DNA inside the cell.

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8
Q

Transformation: Genes activated by Sig H are…

A

proteins that form translocasome complex, which binds to extracellular DNA.

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9
Q

Transformation: Artificial activation of Transformation includes (2) … . The second one is different from processes discussed because…

A
  1. Heat Shock: Short period of high T

2. Electroporation: Small shocks. These do not use C, but the end result is the same transformasome protein.

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10
Q

Transduction: What is Transduction? What’s so special about this in terms of genetic diversty?

A

Using a virus (e.g. phage lambda) as vehicle to move DNA into cell. Sometimes phage DNA may contain some bacterial DNA, thereby incorporating viral and bacterial DNA into a new host.

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11
Q

Transduction: What is a practical application of Transduction in lab?

A

Replace phage DNA with DNA of interest and have the phage work for the scientist.

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12
Q

Conjugation: What is Conjugation?

A

Use of sex pilus as a vehicle to transfer eiher plasmid or chromosome.

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13
Q

Conjugation: The two mating types involved in Conjugation (i.e. Bacterial Mating) are…

A
  1. Donor Cell (F+)

2. Recipeint Cell (F-)

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14
Q

Conjugation: The thing that F+ cells have that F- cells don’t is ___, which also codes for ___.

A

F plasmid (Episome), which also codes for sex pilus

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15
Q

Conjugation: How does Conjugation of F Plasmid work? (Step by step)

A
  1. F+ Cell makes Pilus
  2. Pilus attaches to F- and pulls F- to F+
  3. F+ cell then replicates F plasmid
  4. Replicated F plasmid transfers to F- cell.
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16
Q

Conjugation: What are the three parts of Episome? What do they do?

A
  1. OriT: Origin of transfer
  2. tra Genes: Codes for proteins that make the pilus
  3. OriV: Origin of Replicaion.
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17
Q

Conjugation: What are the 2 differences between donor cell for F plasmid and donor cell for Chromosomal DNA?

A
  1. Chromosomal donor cell called Hfr, not F+

2. Episome integrated in the host genome, not in the cytosol.

18
Q

Conjugation: Why does the F plasmid start as an integrant in the host genome?

A

Integration occurs due to identical sites on F plasmids and bacterial chromosome, called IS (insertion) sites.

19
Q

Conjugation: What is unique about the Conjugation of Chromosomal DNA?

A
  1. Transfer begins at OriT, goes to end of plasmid DNA and then continues into host chromosome. (Hence, not all plasmid gets transferred)
  2. The recipient gets some host chromosomal DNA.
20
Q

Conjugation: What does the Integrant look like? Which genes get transferred first? What function does it have in lab?

A

-[IS]–[TRA]–[IS]–<|—-[IS]—[leu]–[thr]–[ars]
In this case, leu (b/c near the base of the arrow).
Allows for dtection of conjugation in lab.

21
Q

Conjugation: For experiment 10, F- has Str resistance but..

A

needs A.A. for this resistant.

22
Q

Conjugation: For experiment 10, survival means that the cells survived recieved the…

A

DNA and the integrant.

23
Q

Conjugation: The graph of # of colonies v. time for different A.A. genes look like…

A

Log growth with staggered y-intercept.

24
Q

Sexual Mating: Complementation.

Substrate –A–> Intermediate –B–> Product

mutA can’t make __1__ but still has normal __2__.
mutB can’t make __3__ but still has normal __4__.

A
  1. Intermediate (and hence the product)
  2. B
  3. Product
  4. A
25
Q

Sexual Mating: The result of mutA- with mutB- is…

A

(2n) that can make A and B, and hence the product.

26
Q

Sexual Mating: If two mutants, when mated, can make the product, they are thought to __1__ each other and hence belong in ___2___.

A
  1. complement

2. complmentary group

27
Q

Sexual Mating: Complementation.

Substrate –A–> Intermediate –B–> Product

mutB-1 and mutB-2 are in __(same/different)__ complementary group and hence __(can/can’t)__ make the product when mated.

A

Same; can’t

28
Q

Sexual Mating: Mutants in the same complementary group have mutation in the ____.

A

Same gene.

29
Q

Sexual Mating: What are the 7 steps of Complementation Analysis?

A
  1. Take (n) bacteria and mutate them to get 1 random mutation per cell.
  2. Look for mutants unable to make product in question/can’t behave in a certain way.
  3. Mate mutants selected in (2) in pairwise fashion. (i.e. 1x2,1x3, 2x2, 2x3, 3x3)
  4. See where (2n) complement each other. (i.e. expres product/behavior of interest.)
  5. Group mutants into complementation group in which each complementation group represents mutation in specific genes.
  6. # Complementation group = # Genes involved
  7. Sequence genes to I.D. mutated gene.
30
Q

Define Mutation

A

Heritage changes in the base sequence of nucleic acid genome. (Nothing to do with phenotype.)

31
Q

Define + and - Selectable Mutants

A

+ Selective Mutants can grow where WT can’t.
- Selective Mutants can’t grow where WT can, usually due to lacking a specific nutrient. In that case, it is known as an auxotroph.

32
Q

Define Non-selectable Mutants

A

Mutants different from WT in specific characteristics (e.g. size, shape, color).

33
Q

What are the 4 steps of Replica Plating? What is it used for?

A

Used for - Selectable Mutants.

  1. Mature cells
  2. Plate onto media with necessary nutrient (ex. uracil) to grow both WT and Auxotroph.
  3. Transfer colonies with filter paper onto plate with media lacking nutrient to get rid of Auxotrophs.
  4. Compare +uracil and -uracil and pick the “missing colonies”, which are mutants.
34
Q

Mutations: What are two main categories of mutations?

A
  1. Point Mutation

2. Insertion/Deletion

35
Q

Mutations: Point Mutations can lead to 3 different types of mutations, which are… (explain what they are succinctly).

A
  1. Silent Mutation: No effect on AA sequence.
  2. Point Mutation: ∆ AA
  3. Nonsense Mutation: Codes for stop codon (TAG) rather than AA
36
Q

Mutations: Point Mutations, depending on the initial and mutated AA, can either be __1__ or __2__. Examples of these can include (2 for each condition)…

A
  1. Conservative: mut AA similar to original AA (ex. acid to acid or hydrophobic to hydrophobic)
  2. Nonconservative: mut AA is different from original AA (acid to base or hydrophobic to hydrophilic). This has a big impact on protein function.
37
Q

Mutations: Conservative Mutations can lead to ….

A

Thermally Sensitive Protein, in which the protein folds correctly at one T but not at the other.

38
Q

Mutations: Insertion/Deletion Mutations are…

A

Insertions or deletions of N.A. into genome. Deleterious results.

39
Q

Mutations: What is a Reversion?

A

Mutant phenotype leads to WT phenotype.

40
Q

Mutations: What are the two reasons Reversion can occur?

A
  1. Same Site Reversion, where WT genotype is restored at the site of original mutation.
  2. Second Site Mutation, or Compensatory Mutation, where 2nd mutation restores WT phenotype, while genotype is still mutant.

Microbiology (14 decks)

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