Genetic Variation- Bacteria AS (AQA Unit 2) revision

Vertical and Horizontal gene transmission, TB and MRSA

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  • Created by: Sazz
  • Created on: 03-06-09 16:14

Gene Transmission

Bacteria may pass their genes on either by:

Vertical Gene Transmission- Mitosis

Horizontal Gene Tansmission- Conjugation

This can result in mutations, for example resistance to antibiotics, being replicated throughout a whole population.

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1. Conjugation Tubes form between two bacteria, creating a gap in the cell walls for gene transmission

2. The Plasmid, carrying the gene for antibiotic resistance, of the first bacteria begins to replicate

3. As the plasmid replicates it travels down the conjugation tube

4. The replicated strand forms a new plasmid in the second bacteria, meaning this bacteria is also now resistant to antibiotics.

Resistant bacteria are capable of producing enzymes that break down antibiotics and therefore prevent them working

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Antibiotics only kill BACTERIA, not viruses.

They prevent the correct formation of bacterial cell walls, meaing that when osmosis causes the bacteria to become turgid then they burst.

This process is called OSMOTIC LYSIS.

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Resistance to antibiotics is increasing because:

  • TB- Antibiotics are prescribed for tuberculosis. Although the symptoms are reduced after a few days on medication more resistant bacteria are only killed after weeks of taking the medication. Many people stop taking the antibiotics when the symptoms stop, before the course ends. This means only resistant bacteria are left to replicate, resulting in a population of resistant bacteria that are much harder to get rid of.
  • MRSA- Bacteria in hospitals resistant to many antibiotics. This spreads because of a high concentration of antibiotics in hospitals killing non-resistant bacteria. People are also close together, and many people in hospitals have weakened immune systems meaning they are easily infected.
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