Traditionally, machines create designer DNA strands one at a time with many errors. New methods allow the production of millions of strands at once, errors and all. Colors are assigned mechanically to each DNA chemical: adenine, cytosine, thymine and guanine. A laser programmed to analyze the color combinations ignores the erroneous strands and 'prints' the desired ones by separating them from the rest. Uses for designer DNA range from developing color-changing or glow-in-the-dark flowers to designer pharmaceuticals that could possibly eliminate diseases such as Down syndrome and cystic fibrosis.