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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 a mutant?

A

An organism whose genome carries a mutation

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7
Q

What is the phenotype. Eg.

A

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

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8
Q

What is a genomic locus

A

a specific position on a gene

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9
Q

How are mutations named

A

Add number to gene name in order the mutation was isolated
e.g. hisC1

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10
Q

How are modern mutations named?

A

WT base or AA, then muber, then mutant base/AA
eg. HisC (A77K)

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11
Q

How is a deletion mutation shown

A

Delta symbol (deltabtuC)

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12
Q

How are phenotypes named

A

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

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13
Q

What is a point mutation

A

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

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14
Q

What is truncation

A

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

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15
Q

What is a deletion vs insertion mutation

A

Deletion: DNA lost
Insertion: DNA added

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16
Q

What can deletion or insertion mutations lead to

A

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

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17
Q

What is a genetic reversion

A

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

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18
Q

What is a phenotypic reversion?

A

Mutant strain aquires a mutation that reverts it back to the WT phenotype. May be genetic or a new mutation

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19
Q

What is a suppressor mutation

A

Causes phenotypic reversion. Mutation that compensates for the effects of a prior mutation

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20
Q

Give an example of supressor mutation

A

Eg. antibiotic resistance due to outer membrane. Mutant has no outer membrane. Can recreate original WT resistance, not by making an outer membrane, but by breaking down the antibiotic

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21
Q

What are 3 ways we can isolate for mutants?

A

Selection (eg. mutant grows, parent doesn’t)
Abscence of growth
Indicator plates (eg. colour, fluorescence)

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22
Q

What is beta-galactosidase used for in indicators?

A

Can hydrolyze X-gal, which can turn blue

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23
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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24
Q

What is horizontal gene transfer

A

Acquiring new genetic material (foreign DNA) from the environment

25
Q

Three ways foreign DNA can enter prokaryotic cells

A

Transformation
Transduction
Conjugation

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, plasmid)
Be integrated into chromosome (recombination, transposition)

27
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)

28
Q

What is Genetic recombination?

A

Physical exchange of DNA between 2 oarts of the same genome

29
Q

What does homologous recombination do

A

DNA repair mechanism (repairs double strand breaks)

30
Q

How does HR result in genetic recombination?

A

Foreign DNA that is homologous to the host chromosome can be inserted in place of, or in addition to, the native DNA. Leads to deletions, duplications and inversion

31
Q

What is a transposable element

A

Mobile genetic element that contains a transposae gene and inverted repeats

32
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

33
Q

What are the two kinds of transposable elements

A

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

34
Q

What are insertion sequence elements?

A

Have only transposition machinery

35
Q

What are transposons?

A

Contain transposition machinery as well as extra genes (eg. antibiotic resistance)

36
Q

What are transposons used for in lab

A

Generate mutant strains

37
Q

What is Transformation?

A

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

38
Q

Where does the DNA for transformation come from

A

Lysed cells within their environment

39
Q

How does DNA cross the cell membrane

A

Cell needs to actively take it up (regulated process)

40
Q

What is it called when cells can take up free DNA

A

The cell is competent

41
Q

How is DNA captured in competent cells

A

Pili captures it, retracts, one stand of DNA degraded and other passed through CM via a multi protein competence system

42
Q

What are virions?

A

Protein coats that the virus DNA is packaged into

43
Q

What is the lytic pathway?

A

Phage DNA replicated and new particles produced. Virus lyses host cell and is released to infect a new cell

44
Q

What is the lysogenic pathway?

A

Viral DNA is integrated into the host DNA as a prophage. Can become induced into the lytic cycle

45
Q

What is a temperate phage

A

One that can operate via lytic or lysogenic pathway

46
Q

What is transduction

A

Virus transfers bacterial DNA from one cell to another

47
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

48
Q

What is conjugation

A

Horizontal gene transfer requiring cell-cell contact
“mating”

49
Q

What mediates conjugation

A

Conjugative plasmids (F plasmid)

50
Q

What is the F plasmid

A

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

51
Q

What kinds of cells can mate

A

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

52
Q

What kind of pilus do F+ cells encode

A

tra (transfer genes that encode a conjugative pilus that allows F+ and F- cells to attach

53
Q

How is DNA copied in conjugation?

A

The DNA is nicked at the oriT and a single strand is copied

54
Q

What secretion system is used in conjugation

A

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

55
Q

What is an Hfr (high freq recombination) cell

A

Occurs when the F plasmid has an insertion sequence and can integrate itself into the chromosome. Conjugation machinery is still intact, and oriT now on chromosome.

56
Q

What happens when Hfr strains conjugate?

A

Transfer their F plasmid DNA and chromosomal DNA to a F- cell which can be integrated into its genome. It doesn’t transfer the full plasmid though, so the donor is still F-

57
Q

What acquired genes will be maintained

A

Those that provide a selective advantage

58
Q

What is one way to recognize horizontally acquired DNA?

A

Difference in %GC content from the rest of the genome

MICRB 265 (34 decks)

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