AQA AS Biology - DNA and DNA replication (Unit 2)

This Powerpoint presentation should give you the understanding of:

Stucture of DNA

The Triplet Code

DNA and Chromosomes

Replication of DNA

It also contain exam style question with answers.

Goodluck !

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  • Created by: ikram
  • Created on: 13-02-13 22:23

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Ikram Malik…read more

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1.1 Pathogens
· Microorganisms that cause disease are called
· Bacteria and viruses
· Disease is a description of symptoms, either
physical or mental or both. It suggests a
malfunction of the body or mind which can
adverse effect on good health…read more

Slide 3

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Microorganisms as pathogens
For a microorganism to be considered a pathogen it
· Gain entry to the host
· Colonise the tissues of the host
· Resist the defences of the host
· Cause damage to the host tissues.
When and pathogen is transferred from one
individual to another it is known as
"transmission".…read more

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How they get into the body
· By penetrating one of the organisms
interfaces with the environment.
· Skin forms thick, continuous layer and is an
effective barrier to infection.
· Invasion normally occurs when skin is broke.…read more

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Interface entries
· The Gas-exchange system. Pathogens can
cause influenza, tuberculosis and bronchitis in
this way.
· The Digestive system. Food and water may
carry pathogens into the stomach and
intestines via the mouth. Cholera, typhoid and
dysentery pathogen enter this way.…read more

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Prevent entry
· A mucus layer that covers exchange surfaces
and forms a thick sticky barrier that is difficult
to penetrate.
· Enzymes break down pathogens.
· Stomach acid, kill microorganisms.…read more

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this is unit 1 stuff on pathogens??




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