The abo blood group in humans is an example of producing four phenotypes.

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?

Nucleic acids offer variability because they contain alternate forms of genes called .

The basic types of tissue in the human body are