DNA - The source of heredity

The double helix of DNA controls heredity on the molecular level. The hereditary information is stored as the sequence of bases along the polynucleotide chain - a message written in a language of only 4 letters, A, C, G and T. DNA both preserves this information, and uses it. It does this through 2 properties:


1. DNA molecules can duplicate themselves, in a process called replication, in which the 2 halves of the helix separate and a new partner is fabricated to exactly match each half.


2. DNA molecules control the synthesis of the proteins which characterise each type of organism. The structure of DNA directly controls the structure of proteins, and the structure of proteins directly determines the way in which they control living processes. It would appear that biology is increasingly becoming a matter of the shapes and sizes of molecules.