Identical twins are born with black hair. They grow up together as children, but as adults they live far apart and lead very different lives. How do you explain why one of the twin's black hair turns gray over time?

Identical twins came from the same sperm and egg, so they have the same chromosomes and genes. ... As identical twins get older they may look more and more different, because they are exposed to more diverse environments. The science of epigenetics explains how these environmental influences can affect the genes.

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a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.