PETER MENZEL / SCIENCE PHOTO LIBRARY PETER MENZEL / SCIENCE PHOTO LIBRARY
Technician using gel electrophoresis to prepare a DNA sequencing autoradiogram, a technique used to examine the base-pair sequence or chemical blueprint of lengths of DNA. The two strands of nucleotides of which DNA is composed are joined by base pairing; adenine (A) always pairs with thymine (T), guanine (G) with cytosine (C). Hence the base sequence defines a section of DNA. Decoding this sequence is done by electrophoresis through an agarose gel, where fragments of radioactively-tagged DNA separate according to size. The banding pattern (fluorescent pink) is revealed under ultraviolet light. A hard copy is obtained by blotting with radiographic film.
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