Biology- Unit 2- Genetic variation in bacteria

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  • Created by: FireDwarf
  • Created on: 26-03-14 19:03
What is an antibiotic?
Substances produced by living organisims to destroy or inhibit the growth of microorganisms.
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How does a cell wall prevent a cell from bursting?
When water moves into the cell via osmosis it causes pressure which would cause it to burst. The wall is tough and not easilly stretched so the cell wall resists expansion and halts further movement of water,
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What is the name of one of the ways they work?
Osmotic lysis
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How does it work?
Prevents the formation of cell walls by inhibiting the synthesis of the peptide cross-linkages in bacteria cell walls. Weakens the wall, so it stops it withstanding pressure. They are unable to stop H2o entering so osmotic lysis occurs.
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When are they only effective?
When they are growing because the prevent the synthesis and assembly of peptide cross-linkages.
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How do bacteria, without engaging with any others, develop antibiotic resistance?
A random mutation causing a change in its genes, which makes it able to produce an emzyme which breaks down the antibiotic penicillin before it can kill the bacteria.
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The name of the enzyme which is complementary to penicillin?
penicillinase
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Are all mutations good?
No, some of them lead to no advantage while some may be a disadvantage and cause it to die.
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What is vertical gene transmission?
Whena bacterium divides, it will pass on this mutation via its genes onto 2 other bacterium in asexual reproduction.
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What does this cause?
The allele for the gene which causes the enzyme which destroys the antibiotic to increase in frequency. Other types of bacterium die out, causing most to become resistant.
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What is horizontal gene transmission?
Plasmids can be transfered from cell to cell via conjugation. Resistance therefore enters different species of bacterium.
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Superbugs?
if a bacterium species recieved DNA with many mutations due to this horozontal gene transmission, it can be reistant to a range of antibiotics.
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What is the rise in the useage of antibiotics causing?
The more we use antibiotics, the more the bacterium with the resistance will get an advantage over normal ones. This causes the resistant ones to out-compete the normal ones, eventually only leaving us with the resistant antibiotics, spread faster.
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What is conjugation?
When one bacterium cell transfers DNA to another. It is done by one of the cells producing a thin projection that meets the other cell.
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What is this projection called?
Conjugation tube
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What occurs?
Donor cell replicates one of its plasmids and is broken down then to make it linear. It then passes along the tube into the recipient cell. Contact between the cells is brief.
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How is antibiotic resistance linked to tubercolosis?
People take the antibiotics which kills the bacteria present, but stop taking them after a while as the majority are destroyed. Few that remain are most resistant, and these then multiply.
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MRSA?
Is anti-bioitic reistant. Spreads in hospitals because they are weaker, more vunreble to infection. Transfer from nurses and doctors. Many antibiotics, resistant bacteria get more chance to overcome non-resistant and spread therefore faster.
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Card 2

Front

How does a cell wall prevent a cell from bursting?

Back

When water moves into the cell via osmosis it causes pressure which would cause it to burst. The wall is tough and not easilly stretched so the cell wall resists expansion and halts further movement of water,

Card 3

Front

What is the name of one of the ways they work?

Back

Preview of the front of card 3

Card 4

Front

How does it work?

Back

Preview of the front of card 4

Card 5

Front

When are they only effective?

Back

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