All individuals of the first generation of hybrids are identical.
Dominant alleles are usually indicated by capital letters, recessive genes by small letters. In Mendel's experiments purple flowers are dominant, white flowers recessive. In this example R indicates purple, r indicates white.
Each plant receives half its genes from the mother and the other half from the father. Plants with two identical alleles RR or rr are called homozygote, plants with mixed alleles Rr are called heterozygote.
Mendel's first law is illustrated by combining two homozygotes: RR combined with rr results in Rr:
All individuals of the first (F1) generation receive a dominant R allele and a recessive r allele and therefore show the dominant purple colour.
The example above describes the situation with Mendel's garden pea Pisum sativum. In other plants, for example snapdragons, both white and red are dominant traits. If red AA and white BB snapdragons are crossed the result is a blend AB between both colours (pink). Again, all members of the (F1) generation show the same colour:
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