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Biology of Cells 2 > Bacteria and viral genetics > Flashcards

Bacteria and viral genetics Flashcards

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
Q

Bacteria and viral genetics

Transformation

A

When DNA released from dead bacterium into the environment is taken up by another bacteria

26
Q

Bacteria and viral genetics

Transduction

A

Bacterial DNA is transferred between bacteria by bacteriophage virus

27
Q

Bacteria and viral genetics

Selective advantages that may be gained by the transfer of plasmids between bacteria

A

Antibiotic resistance

Synthesis of the pilus

Utilisation of unusal nutrients

Increased virulence

Toxin production

28
Q

Bacteria and viral genetics

What ensures cell-to-cell contact occurs in conjuction and how?

A

Pilus

The pilus of the donor cell recognised receptors on the recipient cell wall

Contracts to create cell-to-cell contact

29
Q

Bacteria and viral genetics

In conjugation does the donor simply give away one of it’s plasmids?

A

No

Replicates the plasmid and transfers the copy

30
Q

Bacteria and viral genetics

Avery, Macleod and McCarty

A

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
Q

Bacteria and viral genetics

Can any bacterial cell acquire genetic material by transformation?

A

No

Only those that have competence factors

32
Q

Bacteria and viral genetics

Steps of transformation

A

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
Q

Bacteria and viral genetics

Horizontal gene transfer

A

Movement of one or more genes from one species to another

34
Q

Bacteria and viral genetics

Vertical gene transfer

A

From mother to daughter cell

35
Q

Bacteria and viral genetics

Major differences between viruses and cells

A

No mitochondria so no biochemical enegry machinery

No ribosomes so no protein synthesis machinery

36
Q

Bacteria and viral genetics

What does HIV target?

A

T helper cells

37
Q

Bacteria and viral genetics

What does the destruction of larger numbers of T helper cells cause?

A

The immune system is seriously comprimised

Become highly susceptible to infections

38
Q

Bacteria and viral genetics

When outside a host a virus is called?

39
Q

Bacteria and viral genetics

When is a virus called a virus?

A

When it is inside a host

40
Q

Bacteria and viral genetics

Basic compostition of a virus

A

Tiny non-living particle

Contains nucleic acid (DNA or RNA) surrounded by a protein coat called a capsid

41
Q

Bacteria and viral genetics

How are viruses classified

A

By their genome, then by the host they infect

42
Q

Bacteria and viral genetics

How are viruses classified by their genome?

A

DNA virus

  • Single stranded (ss)
  • Double stranded (ds)

RNA virus

  • ssRNA
  • dsRNA
43
Q

Bacteria and viral genetics

What classification of virus is HIV (genome)

44
Q

Bacteria and viral genetics

Viruses capsid

A

Protective coat

Built of indentical protein subunits called capsomeres

45
Q

Bacteria and viral genetics

Capsomeres

A

Identical protein subunits that build up the capsid in viruses

46
Q

Bacteria and viral genetics

Enveloped virus

A

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
Q

Bacteria and viral genetics

Basic steps of virus division

A
  1. Attachment to host cell
  2. Entry
  3. Intergration into host DNA
  4. Synthesis of viral components
  5. Viral assembly
  6. Release
48
Q

Bacteria and viral genetics

Retrovirus

A

Virus that has RNA

Must transcribe RNA to DNA by reverse transcriptase enzyme

49
Q

Bacteria and viral genetics

Where does a retrovirus get the reverse transcriptase enzyme from?

A

It is carried inside the capsid

50
Q

Bacteria and viral genetics

Why do retroviruses need to convert their RNA into DNA?

A

Only DNA can be intergrated into the host DNA

Only DNA can be copied by the host DNA polymerase

51
Q

Bacteria and viral genetics

Why is it difficult to create a vaccine for HIV

A

Reverse transcriptase used to convert ssRNA to DNA lacks a proof reading function

This leads to more errors and mutant strains of HIV

52
Q

Bacteria and viral genetics

When does the viruses DNA move into the nucleus

A

When mitosis occurs

53
Q

Bacteria and viral genetics

How is the viruses DNA intergrated into the host DNA

A

Viral enzyme integrase cuts the host DNA

54
Q

Bacteria and viral genetics

Provirus

A

Virus that has been integrated into the host chromosome

Is responsible for synthesis of viral componenets

55
Q

Bacteria and viral genetics

Once the provirus has synthesised new viral components, what happens?

A

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
Q

Bacteria and viral genetics

Transduction

A

Method of introducing genetic diversity into bacteria

Viruses that infect bacteria can transfer bacterial genes from one bacterium to another

57
Q

Bacteria and viral genetics

Two types of virus replication

A

Lysogenic cycle

Lytic infection cycle

58
Q

Bacteria and viral genetics

Lysogenic cycle

A

Type of virus replication

Intergrate into host DNA

Viral DNA is replicated when host divides

Little or no affect to host

59
Q

Bacteria and viral genetics

Lytic infection cycle

A

Type of virus replication

Replicates virus particles within the host cell

Released to infect more host cells

Damages host

60
Q

Bacteria and viral genetics

Viriod

A

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
Q

Bacteria and viral genetics

Prions

A

Non-living infectious particle

Does not contain any nucleic acid (genetic material)

Causes neurodegenerate diseases

Form aggregates in the brain

62
Q

Bacteria and viral genetics

Who carried out the experiment that found bacteria could gain genetic material by transformation

A

Avery, Macleod and McCarty

Biology of Cells 2 (5 decks)

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