deoxyribonucleic acid, the genetic material of all eukaryotes and bacteria and many viruses (see Fig. D63).
Figure D63.

DNA. Electronmicrograph and interpretative drawing of double- and single-strand DNA. (Courtesy of Professor Y. Aloni)

The most direct proof for DNA being the genetic material was provided by genetic transformation. DNA is measured either in base pairs (bp) or spectrophotometrically: 1 unit of optical density (OD) of double-stranded DNA (at 260-nm wavelength) is about 50 μg/mL. One OD of single-strand DNA is about 40 μg/mL; 1 μg/mL DNA contains about 3.08 μM phosphate (DNA types); 3000 nucleotides are about 1 μm in length, 1 pg DNA is about 0.60205 × 1012 Da [10−12/(1.6661 × 10−24 g)]. DNA types. Watson and Crick model, hydrogen pairing, spectrophotomete​r, transformation, xDNA

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