What are some examples of phenotypical characteristics that present two or more varieties and of phenotypical features that do not vary? In relation to the genes correspondent to those characteristics that vary among individuals what can be expected about their alleles?

Color of the eyes, color of the hair, color of the skin, height, blood type are examples of phenotypical features that present two or more varieties. Other examples are the color of flowers and seeds in some plants, the sex of the individual in dioecius species, etc. Examples of phenotypical characteristics that do not present variation among individuals of the same species are: in general the number of limbs, the anatomical position of the organs, the general constitution of tissues and cells, etc.

Phenotype possibility of presenting natural variations (in beings of the same species) are necessarily determined by two or more different alleles of the correspondent gene. These different alleles combine and form different genotypes that condition the different phenotypes (variations).