The information technology of the genes is digital. This fact was discovered by Gregor Mendel in the last century, although he wouldn't have put it like that. Mendel showed that we don't blend our inheritance from our two parents.
Sometimes the genes we receive from our parents can differ at a particular address. When this happens they are known as alleles. How the alleles then interact with each other was explained by Mendel after long study of the colour of pea flowers.
In MendelΓÇÖs peas, flower colour is determined by just one gene. But while the flowers of some pea plants are purple, the flowers of other pea plants are white. These differences arise because the gene for flower colour has two alleles. One allele specifies that the flower will be purple; the other, that the flower will be white. Therefore, a plant that has two alleles for white will have white flowers, a plant that has two alleles for purple will have purple flowers. But what about a plant that has one of each?
It turns out that this individual will also have purple flowers: the allele for purple overrides the allele for white. In this case, purple is said to be ΓÇÿdominantΓÇÖ and white is said to be ΓÇÿrecessiveΓÇÖ.
Not all alleles fall into this pattern, however. For example, snap dragons have flowers that are red, pink, or ivory. This is again due to the action of one gene with two alleles. But while individuals with two ivory alleles have ivory flowers, and individuals with two red alleles have red flowers, individuals with one of each have pink flowers. Then, ivory and red are said to be ΓÇÿpartially dominantΓÇÖ.
