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micro 1 exam 3 > bacterial growth and microbial genetics > Flashcards

bacterial growth and microbial genetics Flashcards

1
Q

what is a pure culture

A

population of organisms descended from a single cell and is therefore separated from all other species

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2
Q

what did Robert Koch develop?

A 
solid media (agar-agar derived from seaweed)
Contained in dishes invented by Kochs lab assistant Julius Richard Petri
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3
Q

What is Binary fission?

A

after a bacterial cell has increased in size and doubled all of its parts, it divides

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4
Q

Define microbial growth

A

an increase in the number of cells in a population

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5
Q

Define generation time

A

time it takes for a population to double in number

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6
Q

Bacterial growth in a lab (a closed system) follows a pattern of stages called _______

A

Growth curve

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7
Q

What are the 4 stages of the growth curve?

A

Lag phase (latent)
Exponential phase (log)
Stationary phase
Death phase

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8
Q

Describe the lag phase (latent)

A

Cells “ramp up” by synthesizing macromolecules required for division & ATP

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9
Q

Describe the exponential phase (log)

A

cells dividing at a constant rate, growth is balanced with available nutrients

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10
Q

Describe the stationary phase

A

cells have exhausted supply of energy and nutrients, number of cells remains relatively constant

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11
Q

Describe the death phase

A

population decreases as cells die off at a constant rate

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12
Q

What are the 2 methods to measure growth?

A
  • direct count method using microscope and hemacytometer

- indirect cell counting using serial dilution

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13
Q

Adenine pairs with?

A

Thymine

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14
Q

Guanine pairs with?

A

Cytosine

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15
Q

A set of 3 nucleotides on a single strand =

A

a codon - this encodes a specific AA

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16
Q

Where does DNA replication begin?

A

replication origin (ori)

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17
Q

Is DNA replication semi-conservative?

A

Yes

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18
Q

What direction does DNA replication proceed in?

A

5’ to 3’

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19
Q

Whats the difference between the leading strand & the lagging strand?

A

Leading strand= continuously synthesized

Lagging strand= discontinous, synthesized in pieces

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20
Q

What are the pieces of the lagging strand called?

A

Okazaki fragments

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21
Q

Describe the central dogma

A

DNA –> (transcription) –> RNA –> (translation) –> protein

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22
Q

Describe transcription

A

mRNA is synthesized from DNA via RNA polymerase
RNA nucleotides are adenine, uracil, guanine, cytosine
new mRNA is moved to ribosomes for translation

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23
Q

Describe translation

A

process of synthesizing proteins
occurs on ribosome
AAs are assembled into growing polypeptide chain (when folded= protein)

24
Q

During transcription what acts as an on/off switch?

A

A regulatory region near the promotor which a regulatory protein can bind to

25
What is an operon?
a set of adjacent genes coordinately controlled by a regulatory protein and transcribed as a single RNA message
26
Is an operon inducible, repressible or both?
Both
27
Genes that are not always being transcribe must be ______ to function
Induced
28
Genes that are always being transcribed must be ______ to prevent proteins from being made
Repressed
29
An inducible operon requires what?
an inducer to prevent a repressor protein from binding to the operator
30
Where does spontaneous mutation occur?
natural environment
31
What is a base substitution?
an incorrect base is incorporated into the DNA during replication
32
Point mutation?
only 1 base is changed
33
Missense mutation?
substitution of different AA in protein
34
Nonsense mutation?
change creates stop codon instead of normal AA coding codon
35
Frameshift?
removal or addition of nucleotides that leads to change in way the DNA sequence is read- changes the codon frame or reading frame
36
Transposones?
segments of DNA that can move spontaneously from one site or another in the same or different DNA molecules aka Jumping genes
37
What is an induced mutation?
a change in DNA sequence that is the result of a mutagen such as radiation or chemical agents
38
What are chemical mutagens?
- they alter the binding of DNA molecule Alkalyting agents base analogs intercalating agents
39
What are the 2 types of radiation?
UV- causes thymine dimers | X-ray- causes single and double stranded breaks in DNA
40
How do we repair mutations?
Bacteria employ mismatch (or excision repair) as well as a mechanism called SOS repair
41
What is a prototroph?
Cells that grow without added growth factors (natural)
42
What is a auxotroph?
Cells that grow only with growth factors added in lab
43
What is a conditional lethal mutant?
Mutants defective for the synthesis of an essential macromolecule under specific conditions
44
What does the term "competent" refer to?
recipient cells that are able to take up DNA | - many populations are naturally competent during log phase of growth
45
How can competence be induced?
CaCl2 or an electrical current = electroporation
46
What are the steps of genetic recombination?
Transformation Conjugation Transduction
47
What are the 2 ways two bacterial cells can contact one antoher?
Plasmid DNA transfer | Chromosomal DNA transfer
48
Describe Plasmid DNA transfer
Plasmid transferred = F plasmid (fertility plasmid) Donor cell containing F is called F+ or male Recipient cell= F- or female F plasmid has series of genes that code for formation of a sex pilus
49
Describe Chromosomal DNA transfer
F plasmid can transfer chromosomal DNA if it integrates into the chromosome and then excises, bringing a portion of chromosome (F' cell) A cell with a F plasmid that has integrated into the chromosome = Hfr cell In order to transfer DNA, a Hfr cell must excise the F plasmid The excised plasmid= F'
50
What is transduction?
Transfer of DNA from cell to cell via a bacteriophage
51
What are the two ways a bacteriophage can interact with cells?
Lytic | Lysogenic
52
Describe Lytic interaction
Phage (virus) overtakes cell Assembly of new phages occur while bacterial chromosmomal DNA may be incorporated Cell lyses to expel new phages containing bacterial DNA phage is capable of transduction
53
Describe Lysogenic interaction
phage (virus) DNA integrates into host DNA (temperate phase) Phage DNA remains in cell for few to many generations Eventually becomes lytic If a viral gene is permanently incorporated into bacterial DNA = lysogenic conversion
54
What is lysogenic conversion
When a viral gene (phage DNA) is permanently incorporated into bacterial DNA. This results in new bacterial strain
55
What are the two types of transduction?
Generalized | Specialized
56
Describe generalized transduction
During production some phages accidentally package only bacterial chromosomal DNA, not viral DNA This phage can still infect cells, but injects bacterial chromosomal DNA into host
57
Describe specialized transduction
The phage packages both viral DNA and bacterial chromosomal DNA It packages specific chromosomal DNA found near where viral DNA integrated during lysogenic phage

micro 1 exam 3 (5 decks)

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