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Biology of Cells 2 > Bacteria and viral genetics > Flashcards

Bacteria and viral genetics Flashcards

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1
Q

Bacteria and viral genetics

Where is the bacterias genes found?

A

It’s circular bacterial chromosome

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2
Q

Bacteria and viral genetics

Where do you find a bacteria’s chromosome?

A

In the nucleoid

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3
Q

Bacteria and viral genetics

How does a bacterial chromosome fit inside the bacteria

A

Compacted by supercoiling

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4
Q

Bacteria and viral genetics

Supercoiling (picture)

A
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5
Q

Bacteria and viral genetics

what controls the DNA twisting in supercoiling of bacterial chromosome?

A

Topoisomerase enzymes

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6
Q

Bacteria and viral genetics

Antibiotics can be used to target what part of the supercoiling process of compacting bacterial chromosomes?

A

Topoisomerase enzymes

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7
Q

Bacteria and viral genetics

At what point of the chromosome does DNA synthesis occur in bacteria?

A

The origin of replication

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8
Q

Bacteria and viral genetics

What term describes the DNA replication in bacteria

  • Meaning
A

Bidirectional

  • Goes both ways from the origin of replication
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9
Q

Bacteria and viral genetics

Bacterial DNA replication (picture)

A
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10
Q

Bacteria and viral genetics

Plasmids

A

Small cicrular pieces of DNA

Can replicate independantly of the bacterial chromosome

Not usually necessary for survival but can provide growth advantages

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11
Q

Bacteria and viral genetics

5 types of plasmid

A
  1. Resistance plasmids (R factors)
  2. Degradative plasmids
  3. Col-plasmids
  4. Virulence plasmids
  5. Fertility plasmids (F factor)
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12
Q

Bacteria and viral genetics

Resistance plasmids

A

Contain genes confer resistance against antibiotics and other types of toxins

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13
Q

Bacteria and viral genetics

Degradative plasmids

A

Carry genes that eneable the bacterium to digest and utilise an unusual substance

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14
Q

Bacteria and viral genetics

Virulence plasmids

A

Carry genes that turn a bacterium into a pathogenic strain

Maybe carrying a capsule protein

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15
Q

Bacteria and viral genetics

Fertility plasmids

A

Allow bacteria to mate with each other

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16
Q

Bacteria and viral genetics

Conjugation

A

Direct physical interaction transfers genetic material from donor to recipient cell

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17
Q

Bacteria and viral genetics

How do bacteria maintain diversity?

A

Mutations that may occur

Genetic transfer between bacteral cells

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18
Q

Bacteria and viral genetics

Induced mutations

A

Mutagens can increase the mutation rate

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19
Q

Bacteria and viral genetics

Mutagens

A

Chemical, biological and physical agents that may increase muation rate

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20
Q

Bacteria and viral genetics

Possible causes of spontaneous mutation

A

Natural radiation

Free radicals from cellular oxidation

Errors during replication

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21
Q

Bacteria and viral genetics

Point mutations

A

Alteration of a base pair of DNA

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22
Q

Bacteria and viral genetics

Frame shift mutations

A

Deletion or insertion of DNA

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23
Q

Bacteria and viral genetics

What is the potential consequences of a mutation?

A

New proteins could be produced

Proteins that don’t function properly are produced

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24
Q

Bacteria and viral genetics

Forms of genetic transfer between bacteria

A

Conjugation

Transformation

Transduction

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25
# Bacteria and viral genetics Transformation
When DNA released from dead bacterium into the environment is taken up by another bacteria
26
# Bacteria and viral genetics Transduction
Bacterial DNA is transferred between bacteria by bacteriophage virus
27
# Bacteria and viral genetics Selective advantages that may be gained by the transfer of plasmids between bacteria
Antibiotic resistance Synthesis of the pilus Utilisation of unusal nutrients Increased virulence Toxin production
28
# Bacteria and viral genetics What ensures cell-to-cell contact occurs in conjuction and how?
Pilus The pilus of the donor cell recognised receptors on the recipient cell wall Contracts to create cell-to-cell contact
29
# Bacteria and viral genetics In conjugation does the donor simply give away one of it's plasmids?
No Replicates the plasmid and transfers the copy
30
# Bacteria and viral genetics Avery, Macleod and McCarty
Found that type-R *Salmonella* doesn't affect mice, but would infect and kill the mice if left in solution with dead type-S of *Salmonella* that does affect mice Concluded that the DNA from type-S was taken up by type-R by transformation
31
# Bacteria and viral genetics Can any bacterial cell acquire genetic material by transformation?
No Only those that have competence factors
32
# Bacteria and viral genetics Steps of transformation
Bacterial cell with competence factors encounters DNA from dead cell DNA fragments bind to bacterial cell surface DNA taken into the cytoplasm Imported DNA incorporated into bacterial chromosome
33
# Bacteria and viral genetics Horizontal gene transfer
Movement of one or more genes from one species to another
34
# Bacteria and viral genetics Vertical gene transfer
From mother to daughter cell
35
# Bacteria and viral genetics Major differences between viruses and cells
No mitochondria so no biochemical enegry machinery No ribosomes so no protein synthesis machinery
36
# Bacteria and viral genetics What does HIV target?
T helper cells
37
# Bacteria and viral genetics What does the destruction of larger numbers of T helper cells cause?
The immune system is seriously comprimised Become highly susceptible to infections
38
# Bacteria and viral genetics When outside a host a virus is called?
A virion
39
# Bacteria and viral genetics When is a virus called a virus?
When it is inside a host
40
# Bacteria and viral genetics Basic compostition of a virus
Tiny non-living particle Contains nucleic acid (DNA or RNA) surrounded by a protein coat called a capsid
41
# Bacteria and viral genetics How are viruses classified
By their genome, then by the host they infect
42
# Bacteria and viral genetics How are viruses classified by their genome?
DNA virus * Single stranded (ss) * Double stranded (ds) RNA virus * ssRNA * dsRNA
43
# Bacteria and viral genetics What classification of virus is HIV (genome)
ssRNA
44
# Bacteria and viral genetics Viruses capsid
Protective coat Built of indentical protein subunits called capsomeres
45
# Bacteria and viral genetics Capsomeres
Identical protein subunits that build up the capsid in viruses
46
# Bacteria and viral genetics Enveloped virus
Has a viral envelope that surrounds the capsid Envelope made up of the lipid bilayer of the host cell This envelope fuses with existing host cell membrane when virsus enters host cell
47
# Bacteria and viral genetics Basic steps of virus division
1. Attachment to host cell 2. Entry 3. Intergration into host DNA 4. Synthesis of viral components 5. Viral assembly 6. Release
48
# Bacteria and viral genetics Retrovirus
Virus that has RNA Must transcribe RNA to DNA by reverse transcriptase enzyme
49
# Bacteria and viral genetics Where does a retrovirus get the reverse transcriptase enzyme from?
It is carried inside the capsid
50
# Bacteria and viral genetics Why do retroviruses need to convert their RNA into DNA?
Only DNA can be intergrated into the host DNA Only DNA can be copied by the host DNA polymerase
51
# Bacteria and viral genetics Why is it difficult to create a vaccine for HIV
Reverse transcriptase used to convert ssRNA to DNA lacks a proof reading function This leads to more errors and mutant strains of HIV
52
# Bacteria and viral genetics When does the viruses DNA move into the nucleus
When mitosis occurs
53
# Bacteria and viral genetics How is the viruses DNA intergrated into the host DNA
Viral enzyme integrase cuts the host DNA
54
# Bacteria and viral genetics Provirus
Virus that has been integrated into the host chromosome Is responsible for synthesis of viral componenets
55
# Bacteria and viral genetics Once the provirus has synthesised new viral components, what happens?
Capsid proteins enclose 2 molecules of viral DNA and 2 molecules of reverse transcriptase Virus buds from plasma membrane of host cell and is released
56
# Bacteria and viral genetics Transduction
Method of introducing genetic diversity into bacteria Viruses that infect bacteria can transfer bacterial genes from one bacterium to another
57
# Bacteria and viral genetics Two types of virus replication
Lysogenic cycle Lytic infection cycle
58
# Bacteria and viral genetics Lysogenic cycle
Type of virus replication Intergrate into host DNA Viral DNA is replicated when host divides Little or no affect to host
59
# Bacteria and viral genetics Lytic infection cycle
Type of virus replication Replicates virus particles within the host cell Released to infect more host cells Damages host
60
# Bacteria and viral genetics Viriod
Infects plant cells Circular ssRNA molecule a few hundred nucleotides in length present in the host cells nucleus Genome does not code for proteins
61
# Bacteria and viral genetics Prions
Non-living infectious particle Does not contain any nucleic acid (genetic material) Causes neurodegenerate diseases Form aggregates in the brain
62
# Bacteria and viral genetics Who carried out the experiment that found bacteria could gain genetic material by transformation
Avery, Macleod and McCarty

Biology of Cells 2 (5 decks)

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