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Micobiology > Chapter 10-Genetics > Flashcards

Chapter 10-Genetics Flashcards

1
Q

Mutation

A

Heritable change in the base sequence of the genome of an organism

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2
Q

Mutant

A

Organism with a mutation, genotype differs from parents

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3
Q

Wild-type

A

Isolated from nature, can be gene or strain

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4
Q

What are some examples of genotype vs. phenotype? How do these examples relate to mutations?

A

The gene for histodinol phosphate aminotransferase, hisC codes for the protein HisC. Mutations in this gene are hisCI and hisC2
His+ and His- do different actions

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5
Q

What does His+ do?

A

Makes own histodine (histodine prototroph)

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6
Q

What does His- do?

A

Cannot make own histidine, requires histidine supplement (histidine auxotroph)

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7
Q

Mutant selection

A

Placing organisms under conditions that favor or inhibit growth of cells with certain phenotypes

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8
Q

Mutant screening

A

Procedure to evaluate many strains, but all strains are able to grow

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9
Q

Is antibiotics resistance selectable or screening?

A

It’s selectable

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10
Q

Is pigment production selectable or screening?

A

Must screen

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11
Q

What are two molecular bases for mutation?

A
  1. Induced-environmental cause

2. Spontaneous-errors in DNA replication

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12
Q

Transition

A

a point mutation that changes a purine nucleotide to another purine (A ↔ G) or a pyrimidine nucleotide to another pyrimidine (C ↔ T).

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13
Q

Transversion

A

the substitution of a (two ring) purine for a (one ring) pyrimidine or vice versa, in deoxyribonucleic acid (DNA).[1]

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14
Q

Frameshifts are due to what?

A

Due to insertions or deletions

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15
Q

Reversion

A

“Back mutation” that restores the original phenotype

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16
Q

Same-site revertant

A

Mutation at same site restores phenotype

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17
Q

Second-site revertant

A

Mutation at different site in DNA restores phenotype-supressor mutation

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18
Q

Supressor mutations

A
  • Mutations in same gene (2nd frameshift mutation)
  • Mutation in another gene that restores function
  • Mutation in another gene that replaces non-functional enzyme with a functional one
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19
Q

Deletions, frameshift mutations are…

A

stable

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20
Q

Insertions are…

A

not as stable

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21
Q

What is removed during direct reversal during DNA repair?

A

An alkyl group

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22
Q

What are three ways of DNA repair?

A
  1. Direct reversal
  2. Repair of single-stranded damage
  3. Repair of double-strand damage
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23
Q

In addition to the removal of an alkyl group, what also happens during direct reversal?

A

Photoreactivation, which cleaves pyrimidine dimers

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24
Q

What is repaired during repair of single-strand damage?

A

Base excision and nucleotide excision

25
Q

How does double-strand damage repair work?

A

Through recombination to repair

26
Q

What is repaired during double-strand repair?

A

Cross-strand links and double-stranded break

27
Q

Describe the rate of changes in mutation.

A

It is low, yet detectable.

28
Q

What organism has enhanced DNA repair?

A

Deinococcus radiodurans

29
Q

In what ways does Deinococcus radiodurans have enhanced DNA repair?

A

20x resistant to UV

200x ionizing radiation

30
Q

What can cause an increased mutation rate?

A

Mutator strains in changing environments

31
Q

What is the Ames Test?

A

It is a mutagenicity test for carcinogens.

32
Q

What does the Ames Test test for?

A

It tests for mutagenic chemicals.

33
Q

How does the Ames Test work?

A

It uses auxotrophs with point mutations so that reversion can occur (His-S. enterica or Trp- E.coli). Also, back mutants have colonies formed on minimal medium and they form more in presence of mutagen

34
Q

Improvements to the Ames test

A
  • Strains that use error-prone repair pathways don’t always give the best reading.
  • Liver enzyme preparations to convert chemicals to active forms needs work.
35
Q

What are 5 kinds of gene transfer?

A
  1. Recombination
  2. Transformation
  3. Conjugation
  4. Transduction
  5. Transposable elements
36
Q

Recombination

A

DNA from two different sources exchange sections or are brought together into a single DNA molecule

37
Q

What is formed by recombination?

A

Homologous DNA

38
Q

How does recombination take place?

A

Crossing over

39
Q

Transformation

A

Free DNA from the environment transforms competent cells

40
Q

First discovery of transformation was by…

A

Frederick Griffith in 1928

41
Q

Transformtion

A

Free DNA from the environment transforms competent cells

42
Q

Transduction

A

Bacteriophage transfers DNA from one cell to another

43
Q

Generalized transduction

A

Any gene on donor chromosome can be transferred

44
Q

Specialized transduction

A

Only a specific set of bacterial genes are transferred due to mistakes in excision

45
Q

Conjugation

A

Genetic exchange involving cell-to-cell contact

46
Q

An F plasmid stands for

A

fertility

47
Q

What can an F plasmid do?

A

Can synthesize F pilus and make able the mobilization of DNA for transfer

48
Q

How is the uptake of another F plasmid prevented?

A

Alteration of surface receptors

49
Q

Episome

A

plasmid that can integrate into the chromosome

50
Q

F+ strain

A

nonintegrated plasmid

51
Q

Hfr strain

A

plasmid integrated into genome

52
Q

Why is gene transfer system development difficult in Archaea?

A

Due to extreme conditions and antibiotics are useless

53
Q

What kind of gene transfer happens in Archaea?

A

Transformation, conjugation, and transduction

54
Q

Mobile DNA, aka

A

transposable elements

55
Q

Transposable elements

A

DNA that moves from one site to another within a DNA molecule

56
Q

What are the insertion sequences of transposable elements like?

A

Short, 1000 nucleotides, inverted repeated of 10-50 base pairs

57
Q

What protein is involved in the insertion sequence formation in transposable elements?

A

Transposase

58
Q

Describe transposons.

A

Large
Inverted repeats
Transposase
Other genes

59
Q

Transposon mutagenesis

A

Selection and screening of treated colonies follow

Micobiology (19 decks)

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