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Heredity
is the way in which characteristics are passed from parents to their children
by the genes. In the 19th century an Austrian monk called Gregor Mendel
discovered the basic rules of how this happens.
Mendel did experiments on pea plants and noticed how the colour and the
height of the plants were inherited. The rules he produced are:
| • | Characteristics
are passed from parents to children by genes - or more accurately
- by alleles |
| • | The
alleles for each characteristic (e.g. pea flower colour) exist in
pairs but they are not quite identical |
| • | If one
of a pair of alleles is dominant then that allele will produce the
observed effect |
| • | In the egg cell or the sperm cell only one allele of a pair is present |
Since Mendel did his work other scientists have found that the same
rules apply to other plants and animals, but for most characteristics,
the contribution of alleles is dependant on a more complex process.