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MICRB 265 > 3-2: Prokaryotic Genetics > Flashcards

3-2: Prokaryotic Genetics Flashcards

1
Q

How are genes named

A

First three letters describe function, fourth designated specific gene
Italicized, last letter capitalized

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2
Q

Example of gene name

A

btuC (Vitamin B12 Uptake, gene C)

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3
Q

How are proteins named

A

Same, but not italicized and first letter also capitalized (e.g. BtuC)

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4
Q

What is a mutation

A

Heritable change in the DNA sequence of a genome (substitution, insertions, deletions)

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5
Q

What is the wild-type strain

A

Strain isolated from nature or parent strain

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6
Q

What is the phenotype. Eg.

A

Observable characteristics of an organism
E.g. metabolic, virulence, morphology

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7
Q

What is a genomic locus

A

a specific position on a gene

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8
Q

How are mutations named

A

Add number to gene name
e.g. hisC1

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9
Q

How is a deletion mutation shown

A

Delta symbol

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10
Q

How are phenotypes named

A

Three letters with (+) or (-) symbol
His+ can make histidine

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11
Q

How do we isolate mutagens

A

Can induce mutations
Can isolate mutants by selection (parent does not grow)

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12
Q

Example of something you can select for to isolate mutant

A

Antibiotic resistance

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13
Q

How do you use indicator plates for screening

A

Phenotype linked to colony appearance (colour, fluorescence)

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14
Q

How do you use indicator plates for screening

A

Phenotype linked to colony appearance (colour, fluorescence)

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15
Q

What is a point mutation

A

Mutation to a single base pair within a protein-coding sequence

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16
Q

What are the three kinds of point mutations

A

Silent (different codon, same aa)
Missense (one aa to a different aa)
Nonsense (change in aa to stop codon; premature end to protein)

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17
Q

What is truncation

A

The premature end to a protein sequence due to a nonsense mutation

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18
Q

What is a deletion vs insertion mutation

A

Deletion: DNA lost
Insertion: DNA added

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19
Q

What can deletion or insertion mutations lead to

A

Frameshift mutation (shifts all downstream codons, scrambles sequence) = disruptive

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20
Q

What is a reversion

A

Mutant that acquires another mutation and reverts back to wild-type

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21
Q

What is a suppressor mutation

A

Mutation that compensates for the effects of a prior mutation

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22
Q

What is the natural mutation rate of prokaryotes

A

10^6 to 10^7 per 1000 base pairs per round of replication

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23
Q

What is horizontal gene transfer

A

Acquiring new genetic material (foreign DNA) from the environment

24
Q

Three ways foreign DNA can enter prokaryotic cells

A

Transformation
Transduction
Conjugation

25
Q

What can happen to the DNA once it is inside the cell (horizontal gene transfer)

A

Be degraded
Replicate as separate entity (phage)
Be integrated into chromosome (recombination, transposition)

26
Q

What can happen to the DNA once it is inside the cell (horizontal gene transfer)

A

Be degraded
Replicate as separate entity (phage)
Be integrated into chromosome (recombination, transposition)

27
Q

Physical exchange of DNA between genetic elements of the same cell

A

Genetic recombination

28
Q

Important type of genetic recombination

A

Homologous recombination

29
Q

What does homologous recombination do

A

DNA repair mechanism (double strand breaks), horizontal gene transfer, genome rearrangements (deletions, insertions)

30
Q

What is the main protein in homologous recombination, what does it do

A

RecA, binds ssDNA, searches for homologous dsDNA, mediates strand invasion

31
Q

What happens during homologous recombination

A

DNA strand from one source (chromosome) fused to DNA strand from another (foreign DNA)

32
Q

What is a transposable element

A

Mobile genetic element, can be inserted into another DNA source

33
Q

What enzyme is involved in transposition. What does it do

A

Transposase enzyme
Recognize inverted repeats, cleaves transposable element of DNA, cleaves another DNA and inserts transposable element into it

34
Q

What are the two kinds of transposable elements

A

Conservative (cut and paste)
Replicative (copy and paste)

35
Q

What are transposons used for in lab

A

Generate mutant strains

36
Q

Process by which free DNA is incorporated into a recipient cell bringing about genetic change

A

Transformation

37
Q

Where does the DNA for transformation come from

A

Lysed cells within their environment

38
Q

How does DNA cross the cell membrane

A

Cell needs to actively take it up (regulated process)

39
Q

What is it called when cells can take up free DNA

A

The cell is competent

40
Q

How is DNA captured in competent cells

A

Pili captures it, retracts, one stand of DNA degraded and other passed through cm

41
Q

What is a bacteriophage

A

Virus that infects bacteria

42
Q

What is a viruses DNA packaged into

A

Virions

43
Q

What are the two bacteriophage pathways

A

Lytic pathway: DNA replicated into new particles using host resources, lyse cell and release to infect new
Lysogenic pathway: viral DNA integrated into host DNA (prophage)

44
Q

What is a temperate phage

A

One that can operate via lytic or lysogenic pathway

45
Q

What is transduction

A

Virus transfers bacterial DNA from one cell to another

46
Q

What are the two kinds of transduction

A

Generalized transduction: during lytic cycle, host cell DNA accidentally packaged into viral particle, injected into new cell

Specialized transduction: after prophage forms, its DNA is excised from genome but some neighboring host DNA is also packaged then injected into new cell

47
Q

What is conjugation

A

Horizontal gene transfer requiring cell-cell contact
“mating”

48
Q

What mediates conjugation

A

Conjugative plasmids

49
Q

What is the F plasmid

A

Fertility plasmid
Strains with F plasmid = F+ = donor cell

50
Q

What kinds of cells can mate

A

F+ (donor) and F- (recipient) only

51
Q

What kind of pilus do F+ cells encode

A

Conjugative pilus

52
Q

What does the conjugative pilus do

A

Attaches to other cell, brings them together, forms conjugative bridge

53
Q

What secretion system is used in conjugation

A

Type four
Transfers F plasmid DNA from F+ cell to F- cell

54
Q

What is an Hfr cell

A

Insertion sequence of F plasmid integrates into chromosome of recipient
Part of donors chromosomal DNA transferred
Donor DNA incorporated into recipient genome
Full F plasmid not transferred, recipient is still F-

55
Q

What acquired genes will be maintained

A

Those that provide a selective advantage

56
Q

What happens to most acquired DNA

A

Lost

MICRB 265 (34 decks)

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