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DNA (Deoxyribonucleic acid) provides the genetic information necessary for the development and reproduction of all living organisms and is often described as a genetic blueprint.[1] Every living organism has its own DNA code that is organized in the ladder-like structure of the DNA molecule as a series of complementary paired molecules called bases. DNA is found within the nucleus of many cells, including those of animal and plant life.
 Shown here are the four "letters" of DNA. Each single strand of DNA is a long biopolymer composed of repeating units called nucleotides. A nucleotide is a base linked to a sugar and phosphate group which form a sugar/phosphate backbone. Attached to each sugar molecule (deoxyribose) is one of the four bases:
The corresponding deoxynucleosides are:
- Deoxyadenosine[6]
- Thymidine[7]
- Deoxyguanosine[8]
- Deoxycytidine[9]
Nuclear DNA is organized and stored as chromosomes within the nucleus. The nucleus is a double membrane separating the DNA from the cytoplasm of the cell enabling certain processing to occur prior to protein synthesis. Each chromosome holds hundreds or thousands of genes. A gene can be described in different ways but in general can be thought of as a whole unit of genetic information.
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