Blackwell Publishing



The molecule called DNA (deoxyribose nucleic acid) provides the physical mechanism of heredity in all living creatures. The DNA carries the information used to build a new body, and to differentiate its various body parts. DNA molecules exist inside almost all the cells of a body, and in all the reproductive cells (or gametes).

The DNA molecule consists of a sequence of units; each unit, called a nucleotide, consists of a phosphate and a sugar group with a base attached. There are four different bases: adenosine, cytosine, thymine and guanine. Triplets of bases, called codons, code for amino acids.

The DNA in an individual human cell contains two sets because of diploidy, each about three billion nucleotide units. The total length can be divided into genes and other kinds of DNA.

In most cells, the DNA physically is carried in structures called chromosomes. The molecular structure of DNA was worked out by Watson and Crick in 1953.

As Richard Dawkins explains, DNA is the information used to build a new body, but we should not regard it as the blueprint of an organism.

An animation illustrates how genetic material is structured.

How does the DNA encode the information to build a body?

Previous Next