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DNA research. Conceptual imagery of research into DNA (deoxyribonucleic acid), the chemical molecule which carries the genetic code. The sequence of bands and letters represent a sequence of the four nucleotide bases (C, T, A and G) that connect the two helical strands that make up DNA. It is the arrangement of these four bases along the DNA strand that codes the genetic information. This sequence can be studied and linked to hereditary traits and illnesses. DNA also codes the sex of an individual as represented by the circular male (arrow) and female (cross) symbols. Blood samples can be taken with a syringe, though all cellular material contains DNA. (KEYSTONE/SCIENCE PHOTO LIBRARY/RICHARD PRIDEAUX)