Location: suspended from the ceiling of the rotunda, Building 38

Constructed especially for the National Library of Medicine by Mr. A. A. Barker of Cambridge, England.

The DNA model was originally placed here as part of "The Genetic Code...and How It Works," (1969), an exhibit which centered on the work of Nobel Laureate, Dr. Marshall W. Nirenberg of the National Institutes of Health, the first Federal scientist to be awarded a Nobel Prize.

Constructed around a stainless steel tube, this model is an idealized piece of DNA which contains information that can be translated into directions for forming a messenger RNA (ribonucleic acid) and specific amino acid sequence in a protein. Plastic balls of different sizes represent hydrogen (white); oxygen (red); nitrogen (blue); carbon (black); and phosphorus (purple), the only atomic constituents of these enormous molecules. The molecular weight of this piece of DNA approximates 35,000 whereas the molecular weight of the chromosomal DNA from e. coli is 2,000,000,000 and is actually 10,000,000 angstroms long and 20 angstroms wide. (An angstrom is a unit of length equal to one tenth of a millimicron or one ten-millionth of a millimeter and is primarily used to express electromagnet wavelengths.) The complete DNA molecule on the scale of this 15 foot high model would be 142 miles long.

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Last Reviewed: February 27, 2012