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Genetic Analysis of Bacteria > Condition Mutations > Flashcards

Condition Mutations Flashcards

1
Q

What are non-conditional mutations?

A

Display mutant phenotype under all conditions, regardless of environment or temperature or medium

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2
Q

What is a null mutation?

A

Complete knockout

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3
Q

What is a leaky phenotype?

A

Partial mutant phenotype

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4
Q

What are conditional mutations?

A

Only displays the mutant phenotype under certain environmental conditions

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5
Q

What are permissive conditions?

A

Conditions that allow the mutants to survive and grow and behave like WT cells

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6
Q

What are restrictive conditons?

A

Conditions that show the mutant phenotype

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7
Q

Why are conditional mutations important for studying genetics in bacteria and phages?

A

Only way to study essential genes, since its the only way to study a lethal mutation

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8
Q

What are 3 commonly used conditional mutations?

A

Auxotrophs
Temperature sensitive
Suppressor sensitive

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9
Q

What is an auxotroph?

A

The mutant lacks the ability to synthesize a compound required for growth

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10
Q

What are permissive conditions for an auxotroph?

A

Rich medium or supplemented minimal medium with the thing the cell can’t make

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11
Q

What are restrictive conditions for an auxotroph?

A

Minimal media

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12
Q

What happens at different temperatures for a non-lethal temp sensitive mutant?

A

Shows a different phenotype like a colour change at high temps vs at low temps, but the cell/virus doesn’t die

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13
Q

What are the permissive conditions for a non-lethal temp sensitive mutant?

A

Low temps

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14
Q

What are the restrictive conditions for a non-lethal temp sensitive mutant?

A

High temps

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15
Q

What is a conditional lethal temp sensitive mutant?

A

Contains a temp sensitive mutation in an essential gene. Cells die in restrictive conditions

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16
Q

What are the permissive conditions for a conditional lethal temp sensitive mutant?

A

Low temps

17
Q

What are the restrictive conditions for a conditional lethal temp sensitive mutant?

A

High temps - they die

18
Q

Why is the higher temp the restrictive condition for a temp sensitive mutant?

A

These mutations cause the protein to be destabilized at higher temps

19
Q

How would you look for temp sensitive mutations in a particular pathway?

A
  1. Mutagenize the cells
  2. Plate under permissive conditions so all cells, mutant and WT survive
  3. Replica plate onto restrictive conditions
  4. Compare the plates and look for something that looks different or doesn’t grow in the restrictive conditions
20
Q

How does the FluMist vaccine work?

A

The virus is live, but has a temp sensitive mutation that stops it from replicating at high temps. Your nose is a low enough temperature that the virus can replicate enough to stimulate an immune response, but if it gets in your lungs it becomes inactive so you can’t get sick. Because the virus is live and not injected it can get into other people’s noses and they create antibodies against it too

21
Q

What are suppressor sensitive mutations?

A

Informational suppressor mutation

22
Q

What are the permissive conditions for suppressor sensitive mutations?

A

A strain of bacteria carrying the suppressor. The WT phenotype shows

23
Q

What are the restrictive conditions for suppressor sensitive mutations?

A

A WT strain of bacteria with no suppressor. The mutant phenotype will show

24
Q

What are nonsense suppressors?

A

Original mutation is a nonsense mutation, and the suppressor is in the anticodon of the tRNA that causes the stop codon to be misread as an AA

25
Q

Do nonsense suppressors tend to put the right AA in place of the nonsense mutation?

A

Not usually

26
Q

What is the problem with nonsense suppressors?

A

Causes a bunch of other stop codons to be misread, which causes stop codons where the protein is actually supposed to stop to be missed, and a bunch of proteins end up longer than normal

27
Q

Do nonsense suppressor strains grow very well?

A

No, they grow slowly even on rich media because a bunch of proteins are being slightly messed up

28
Q

Does a single nonsense suppressor work for all nonsense mutations?

A

No, depends on which stop codon it is. A suppressor will only fix one stop codon

29
Q

What are the names for the 3 stop codons?

A

Amber, ochre, opal

Genetic Analysis of Bacteria (10 decks)

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