Microbial Genetics Flashcards
(163 cards)
0
Q
What does adenine pair with?
A
Thymine (A-T)
1
Q
What 4 nucleotides compose DNA?
A
Adenine, thymine, guanine, cytosine
2
Q
What does guanine pair with?
A
Cytosine (G-C)
3
Q
How many nucleotides are on a single strand? And what do they code for?
A
A set of 3 nucleotides on one strand
Encodes for specific AA.
4
Q
Where does DNA replication begin?
A
At a specific nucleotide sequence called a replication origin.
5
Q
Where does synthesis occur, and what does it use?
A
On both strands using a variety of enzymes and proteins
6
Q
DNA replication is semi ______?
A
Conservative
7
Q
Which direction does replication proceed in?
A
5’ to 3’ direction on DNA strand.
8
Q
What is the leading strand?
A
The single strand that is synthesized continuously during DNA replication.
9
Q
What is the lagging strand?
A
The strand that is synthesized discontinuously in pieces during DNA replication.
10
Q
What are the “pieces” on the lagging strand called?
A
Okazaki fragments.
11
Q
Where does information from DNA pass to during gene expression?
A
To an RNA copy of the gene
12
Q
What does the RNA copy direct?
A
The sequential assembly of a chain of AAs.
13
Q
What is the path of the central dogma?
A
DNA —> (transcription)—> RNA —> (translation)—> protein
14
Q
What are the 3 steps in transcription?
A
1) mRNA (messenger) is synthesized from DNA template by RNA polymerase
2) RNA nucleotides are adenine, uracil, guanine, cytosine
3) the newly created mRNA is immediately moved to ribosomes for translation.
15
Q
What is translation?
A
Process of synthesizing proteins that occurs simultaneously with transcription.
16
Q
Where does translation occur?
A
On ribosomes
17
Q
How are the AAs assembled in translation?
A
Into growing polypeptide chain (when folded = protein)
18
Q
How many genes are encoded on a single RNA in bacteria?
A
Bacteria frequently have more than one gene encoded on a single RNA using only one promotor
19
Q
What controls transcription of genes?
A
Often controlled by means of a regulatory region, acts as an on/off switch.
20
Q
Where is the regulatory region located?
A
Near the promotor, which is where a regulatory protein can bind.
21
Q
What is the term for the following definition?: a set of adjacent genes coordinately controlled by a regulatory protein and transcribed as a single RNA message.
A
Operon
22
Q
Operons are ______ or _______
A
Inducible or repressible
23
Q
What does an inducible operon require?
A
And inducer to prevent a repressor protein from binding to the operator.
24
What does the repressible operon require?
That the operator be bound by a repressor
25
What is the term for the following description? End product inhibit enzymes early in pathway preventing production of the end product
Feedback inhibition
26
Where do spontaneous mutations occur?
In the natural environment
27
What is the term if only one base is changed?
Point mutation
28
Define missense mutation
Substitution of different AA in protein
29
What type of mutation occurs If change creates stop codon instead of normal AA coding codon?
Nonsense mutation
30
What does a removal or addition of nucleotides lead to?
Change in the way the DNA sequence is read - changes the codon frame or reading frame --> frame shift
31
What are transposons, and what are the AKA?
Segments of DNA that can move spontaneously from one site to another in the same or different DNA molecule.
Aka - jumping genes
32
What is an induced mutation?
A change in DNA sequence that is the result of a mutagen such ad radiation or chemical agents
33
What do chemical mutagens do to DNA?
Alters the binding of the DNA molecule.
34
What are 3 kinds of chemical mutagens?
Alkylation agents
Base analogs
Intercalating agents
35
What 2 types of radiation cause mutations?
UV
| X-ray
36
What does uv light cause?
Thymine dimers
37
What does X-ray radiation cause to happen to DNA ?
Causes single and double stranded breaks in DNA
38
How are mutations repaired?
Bacteria may employ mismatch (or excision repair) as well as SOS repair.
39
What is mutant selection?
In order to study the function of various genes investigators induce mutations and select specific types of mutants to help understand the normal gene function.
40
What are two types of nutritional mutants?
Prototroph
| Auxotrophs
41
Cells that grow without added growth factors (natural strains) are called what?
Prototrophs
42
What are cells that grow only with growth factors added in the lab called?
Auxotrophs
43
What are conditional lethal mutants?
Mutants defective for the synthesis of an essential macromolecule under specific conditions.
44
Who first demonstrated transformation?
Griffith.
45
What did Griffith recognize?
Some unknown compound was transforming bacterial cells (later identified as DNA)
46
What happens as cells die and burst?
DNA is released
| *dna is not contained in a cell, it is "naked" *
47
What does a competent cell mean?
Recipient cell is able to take up DNA.
| *mechanism of competence is poorly understood, many populations are naturally competent during log phase of growth*
48
How can competence be induced in any cell?
By treatment with CaCl2. Or by subjecting cells to an electrical current, called electroporation.
49
What does conjugation require contact between?
The two bacterial cells.
50
What two ways can DNA be transferred during conjugation?
1) plasmid DNA
| 2) chromosomal DNA
51
Which plasmid is transferred in plasmid DNA transfer?
The F plasmid (fertility plasmid)
52
What is the donor cell called in plasmid DNA transfer?
The donor cell containing the F plasmid is called F+ or male.
53
What is the recipient cell in plasmid DNA transfer called?
F- or female.
54
What does the F plasmid series of genes code for?
Formation of a sex pilus
55
When can the F plasmid transfer chromosomal DNA?
If the F first integrates into the chromosome then excises, bringing a portion of chromosome (F' cell)
56
What is an Hfr cell?
A cell with a F plasmid that has integrated into the chromosome.
57
What must the Hfr cell do in order to transfer DNA?
Excise the F plasmid. The excised plasmid is termed F' (F prime)
58
What is transduction?
Transfer of dna from cell to cell via a bacteriophage.
59
What two ways do bacteriophages interact with cells?
Lytic
| Lysogenic
60
What happens during lytic interaction? (Long answer, sorry)
- phage (virus) overtakes cell
- assembly of new phage, and bacterial chromosomal DNA may be incorporated
- cell lyses to expel new phages containing bacterial DNA - phage is capable of transduction
61
What happens during lysogenic interactions?
- phage 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 called lysogenic conversion
- results in new bacterial strain.
62
What are the two types of transduction?
Generalized and specialized.
63
What is packaged during generalized transduction?
During production soe. Phages accidentally package only bacterial chromosomal DNA and not viral DNA in capsid.
64
What does the phage do during generalized transduction after packaging is completed?
This phage can still infect cells, but injects bacterial chromosomal DNA into host
65
What does the phage package during specialized transduction?
Both viral DNA and bacterial chromosomal DNA
66
Where does the phage of specialized transduction find the chromosomal DNA ?
Near where viral DNA integrated during lysogenic phase.
67
What was the beginning of the era of recombinant DNA technology?
The discovery of restriction endonucleases in bacteria.
68
Why are all the cells of E. Coli called a DNA library?
Because each cell contains a portion of the total genome of the organism.
69
What are the applications of genetic engineering for biotechnology?
1) stimulate bacterial cells to produce protein products not normally produced.
2) insulin is now mass produced in E. Coli (so it HGH, IFN, f.8)
3) produce subunit vaccines
4) replacement therapy)
70
What is a subunit vaccine composed of?
Purified antigenic determinant that is separated from the disease causing organism
71
What is substituted in replacement therapy?
Less virulent microbes for virulent strains.
72
What is the term for a result of treatment in a hospital or hospital-like setting, but secondary to the patients original condition.
Nosocomial infection
73
What does iatrogenic infection mean?
"Brought forth by a healer". Used to refer illness caused by or resulting from medical treatment.
74
What are 4 sources if iatrogenic/nosocomial infections?
- direct contact by touching
- contaminated fomites
- contact with contaminate fluids
- airborne transmission.
75
What are a few ways to prevent and control iatrogenic and nosocomial infections?
Disinfection/ antiseptic
Hand washing
Monitoring patient population
76
Define sterilization
Absence of all life
77
Define disinfection
Killing/removing pathogens
78
Define antiseptic
Disinfectant applied to tissue
79
What is a substance that kills/removes only bacteria?
Bactericide
80
What is a severe infection leading to a systemic immune response?
Sepsis
81
Define asepsis
Using aseptic technique
82
Define microbiostasis
Inhibition of microbe growth
83
What is a range of activity against microbes know as?
Spectrum
84
Define activity
Drugs tested to determine the lowest concentration that inhibits microbe called MIC (minimum inhibitory concentration)
85
What is combination therapy?
Use of more than one antibiotic to increase spectrum or killing effect
86
What is "increased killing effect by using multiple antibiotics" ?
Synergism
87
What is antagonism?
1 antibiotic interferes with the action of another
88
What are three methods of sterilization?
```
Moist heat (steam, boiling water)
Autoclave (steam with pressure)
Dry heat (yflame, oven)
```
89
What are 5 kinds of antibiotics?
- inhibitors of cell wall synthesis
- inhibitors of cell membrane
- inhibitors of protein synthesis
- inhibitors of nucleic acid synthesis
- antimetabolites
90
What do inhibitors of cell wall synthesis prevent?
Cross-linking of peptidoglycan by binding to enzyme receptor sites
91
What are 5 kinds of inhibitors of cell wall synthesis antibiotics?
- penicillins and derivatives
- cephalosporin
- bacitracin
- vancomycin
- isoniazid
92
Describe the characteristics of penicillins
Beta-lactam chemical structure
93
Which kind of bacteria are resistant to penicillin?
Bacteria that produce enzyme beta-lactamase
94
What structure do cephalosporins have?
Beta-lactam chemical structure
95
How are derivative of cephalosporin grouped?
Into generations by their antimicrobial properties
96
Which bacteria are resistant to cephalosporin?
Bacteria that produce enzyme beta-lactamase
97
What is the first step in DNA replication?
Opening the DNA helix
98
What is the 2nd step in DNA replication?
Building primers
99
What is the 3rd step in DNA replication?
Assembly of complementary strands (A-T, G-C)
100
What is the 4th step in DNA replication?
Remove primers and join Okazaki fragments.
101
what is bacitracin toxic to? and how is it used?
toxic to kidneys
| used topically only
102
what does vancomycin fight?
initially staphylococcus aureus
| treats systemic infections
103
what is vancomycin toxic to and what is the result?
damage to kidneys
nerve deafness
skin rashes
thrombophlebitis
104
What does isoniazid inhibit?
synthesis of mycolic acids in cell walls of myobacteria
105
What is isoniazid active against?
myobacteria only
106
Which antibiotic is an inhibitor of cell membrane?
polymyxin B and E
107
What does polymyxin B and E replace?
replaces Mg2+ and Ca2+ from membrane lipids disrupting the structure of the bacterial cell membrane
108
How is Polymyxin used?
only topical use. it is quite toxic
109
What are 4 kinds of inhibitors of protein synthesis antibiotics?
Streptomycin
Tetracycline
Chloramphenicol
Erythromycin
110
Are all inhibitor of protein synthesis antibiotics broad spectrum?
yes
111
Which inhibitor of protein synthesis antibiotics are bacteriostatic?
Tetracycline
Chloramphenicol
Erythromycin
112
When is streptomycin used?
in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects
113
What are two derivatives of streptomycin?
kanamycin
| gentamycin
114
What can tetracycline cause?
photosensitivity, renal toxicity, and stains teeth particularly in young children
115
What can chloramphenicol cause?
toxic, can cause aplastic anemia
116
Who is erythromycin typically given to?
people allergic to penicillin
117
Is erythromycin toxic?
mildly
118
What are two inhibitor of nucleic acid synthesis antibiotics?
Rifampin
| Quinolones (fluoroquinolones)
119
What is rifampin used to treat, and is it toxic?
treats TB in combination with other antibiotics
| NOT toxic
120
What do quinolones inhibit?
DNA replication, bacteriocidal
121
What is a common example of quinolones?
Ciproflaxin
122
What kind of antibiotic is sulfonamides (sulfa drugs)?
antimetabolite
123
What are sulfa drugs a precursor to?
antibiotics, antimicrobial agents derived from sulfonic acid
124
What do sulfa drugs inhibit?
folic acid synthesis
125
Are sulfa drugs bacteriostatic?
yes
126
Are sulfa drugs wide spectrum?
yes
127
What kind of infections do sulfa drugs fight?
protozoa infections
128
What is an example of sulfa drugs and what does this one treat?
Dapsone
| treats myobacterium leprae (leprosy)
129
What are 5 clinical problems associated with antibiotic use?
- infection continues even if symptoms subside
- affects normal flora
- microbes become resistant
- toxicity, not often seen, but possible
- sensitization, develop rashes, fever, anaphylaxis
130
What is penicillin a derivative of?
Molds
131
What does penicillin cause enzymes in cell to do?
Lyse
132
What kind of infections is penicillin used for?
G+ bacterial infections
133
Is penicillin broad spectrum?
No
134
Are any forms of penicillin broad spectrum?
Yes - ampicillin works on G+ and G-
135
What is bacitracin developed from?
Bacillus
136
What does bacitracin interfere with?
Peptidoglycan wall assembly
137
Is bacitracin effective against G- or G+?
Primarily G+
138
What is vancomycin developed from?
Streptomyces
139
What does vancomycin interfere with?
Lipid/peptidoglycan building
140
What was vancomycin initially used to treat? And primarily?
Staph aureus
| Systemic infections/heart valve infections
141
What is isoniazid active against only?
M. Tuberculosis
142
Is isoniazid bactericidal?
Yes
143
Is isoniazid bacteriostatic?
Yes, if mycobacterium is slow growing
144
What is isoniazid toxic to?
Liver
| Peripheral nerves
145
What type of antibiotic is polymyxin B and E?
Cell membrane disrupters
| Cationic detergent
146
What is the general structure of polymyxin B and E?
Cyclic peptide with long hydrophobic tail
147
What is polymyxin most effective against?
G-
148
Is polymyxin toxic?
Yes. Highly neurotoxic and nephrotixic
| Very poorly absorbed by GI
149
What was the first antibiotic remedy for TB?
Streptomycin
150
Which class of drugs is streptomycin in?
Aminoglycosides
151
What kind to antibiotic is spectinomycin?
Protein synthesis
152
Is spectinomycin broad spectrum? Is it bacteriostatic?
No
| No
153
Which antibiotic is spectinomycin similar to?
Chloramphenicol but less toxic
154
What is spectinomycin used to treat?
Pencilling resistant gonorrhea
155
What does rifampin bind to?
RNA polymerase inhibiting transcription
156
What is quinolones active against?
Mainly G- , used to treat pseudomonas infections
157
What is a side effect of quinolones?
Mild GI upset.
158
Are sulfonamides wide spectrum? Bacteriostatic?
Yes
| Yes
159
What kind of antibiotic is trimethoprim/nitrofurantoin?
Antimetabolites
160
What does trimethoprim/nitrofurantoin inhibit?
Folic acid synthesis
161
Are trimethoprim/nitrofurantoin broad spectrum? Bacteriostatic?
Yes
| Yes
162
What does trimethoprim/nitrofurantoin treat?
Used in prophylaxis and treatment of uti (cystitis)
