Genetic Variation in Bacteria

This is a summary on genetic variation in bacteria.

Including an experiment which has been carried out to prove that conjugation occurs.

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Genetic Variation in Bacteria
Through the process of natural selection, species
change to adapt to their environment ­ essential for
reproduction and continuation of a species, this is
known as adaptation.
This can happen in two ways:
Mutation ­ this is when one code in a DNA
sequence is deleted, changed or added.
Because DNA codes for amino acids,
therefore proteins and proteins lead to
making us the way we are, it changes an
organisms characteristics
Reproduction ­ Recombining existing DNA
of two individuals
A way of seeing adaptation is by looking at
antibiotic resistance in bacteria.
Conjugation is a way of transferring DNA to another bacterial cell. It occurs in the
following steps:
A thin projection from cell meets another cell and a conjugation tube is
formed between one bacteria and the other
Plasmids from the resistant bacteria are replicated and broken so that
they are linear do that they canpass through the tube
The new bacteria now has the DNA to be resistant to the antibiotic
The amount of contact is kept to a minimum ­ just enough to pass on the
There's 2 types of transmission ­ horizontal where DNA is passed from one
species to another through conjugation
vertical where DNA is passed down
generations through reproduction
Discovering conjugation
Joshua Lenderberg was a medical student who tested DNA been passed to
other bacterial cells. He gathered 2 strains of bacteria, strain one could not
develop 2 amino acids which it needs to grow and strain two could not develop
another 2 amino acids which it needs to grow. The experiment is summarised
on the following page:

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1. Both strains were growing in mediums which helped them survive
2. They were then added to a minimal medium (without any supplements)
3. There was no growth on any of the mediums, this can be explained
because they don't have the ability to synthesise amino acids
4. The two strains were then mixed together and grown in a medium which
contained supplements of all of the missing nutrients
5.…read more


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