The system of organs including the nose, mouth, trachea, bronchi, bronchioles and alveoli through which air is taken into the body
A general name for the processes which scientists use to produce desired characteristics or substances that are in short supply, such as human insulin.
The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell
A viral infection of the breathing system which attacks the lungs and can be fatal
Viruses are very tiny – they are much smaller than bacteria or fungi . They measure only a few thousand millionths of a metre (nanometres).
All natural viruses cause disease including the common cold, influenza (flu), measles, mumps and rubella. They are not living cells themselves, and they can only reproduce inside other living cells.
Viruses can attack all different types of living organisms – they invade animal, plant and even bacterial cells. Different viruses attack specific cells – so the 'flu virus attacks the cells of the respiratory system while the virus which causes meningitis attacks the cells of the membranes which cover your brain.
Scientists have started to use viruses to benefit people. They are an important tool in genetic engineering. They are used to carry new genes into the DNA of the cells of other organisms.
The flu virus
Photo provided by CDC/ Dr. Erskine. L. Palmer; Dr. M. L. Martin
The structure of a virus