Genes are composed of DNA, which encodes the information needed for living cells to make proteins. In human beings, this relationship is seen in the form of inherited traits, such as eye or hair color. In microorganisms, like bacteria and yeast, genetic traits usually appear as biochemical characteristics, such as the ability to grow on one sugar but not another.

The DNA of many organisms, including animals, yeasts and fungi, is found inside the cell nucleus. These organisms as a group are referred to as eukaryotes, which means "true nucleus." In eukaryotic cells, the DNA can also be found in larger structures called chromosomes, which in some cases can be seen through a microscope during cell division. Some chromosomes have a distinct, familiar "X" type structure.

Unlike eukaryotic cells, bacterial cells do not have a defined nucleus. In addition, the bacterial chromosome consists of a single large circle of DNA, rather than the distinct superstructure associated with higher organisms. Because of the lack of a nucleus, bacteria are categorized as a separate group of organisms called prokaryotes.

In all organisms, the entire genetic complement of a single organism -- the sum of all of its genes -- is referred to as the genome. (You have heard this term in relation to the Human Genome Initiative, an ambitious international effort to identify, clone and sequence every human gene).

While we do work with DNA at Amgen, our principal interest lies in proteins, the workhorse molecules of the cell. Proteins have a number of uses within the body. Hormones act as cellular messengers, while the cytoskeleton makes up structural components. Enzymes are mediators of the cell's metabolism, and antibodies and lymphokines are major components of the body's immune response.

As a result of their biological significance, proteins can make excellent drug candidates when we capitalize on their natural functions. Genes, in the form of DNA, are our basic instructions in creating proteins of interest.