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Slide 2

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General Introduction
· Through natural selection, organisms adjust to suit the changing
environmental conditions. This is known as adaptation.
· Adaptation increases the long-term reproductive success of a
species by helping its members to survive long enough to breed.
· Adaptation & selection are major factors in evolution.
· They make a significant contribution to the diversity of organisms.
· One of the most diverse & adaptable group of organisms ­
· Their adaptation to a changing environment can be seen in their
ability to develop resistance to antibiotics.…read more

Slide 3

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How does variation arise in bacteria?
· DNA is the genetic material in Bacteria.
· Diversity in bacteria arises from changes to its DNA.
· These changes occur in two ways:
~ changing the quantity or structure of DNA ­ Mutation
~ recombining the existing DNA of two individuals ­ Conjugation…read more

Slide 4

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· Mutations are changes in DNA that result in different characteristics.
· Mutation arise in many ways. For example, one or more bases in a
DNA may be added, deleted or replaced during DNA replication.
· Any differences in the base sequence of a DNA molecule may result
in a different sequence of amino acid being coded for.
· This different amino acid sequence will lead to a different
polypeptide, and hence a different protein, or no protein at all,
being produced.
· If this protein is an enzyme it is likely to disrupt the metabolic
pathway leading to the production of other substances.
· As proteins are responsible for the characteristics of an organism, it
follows that changes to DNA are likely to alter an organism's
characteristics.…read more

Slide 5

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Bacterial conjugation is the transfer of genetic material between
bacterial cells by direct cell-to-cell contact or by a bridge-like
connection between two cells. It takes place as follows:
· One cell produces a thin projection that meets another cell & forms a
thin conjugation tube b/w the two cells.
· Donor cell replicates one of its small circular pieces of DNA
· Circular DNA is broken to make it linear before it passes along tube.
· Replicated plasmid starts to move through conjugation tube and the
linear strand enters recipient cell.
· Linear strand forms a circle (new plasmid).
· Recipient cell acquires new characteristics from the donor cell.
com/sites/dl/free/0072835125/126997/animation6.html…read more

Slide 6

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Transfer of DNA in the form of genes from one species to another (by
conjugation) ­ Horizontal gene transfer
· Transfer of genes from one generation to the next generation of the
same species ­ Vertical gene transfer ­ occurs when an organism
receives genetic material from its ancestor…read more

Slide 7

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