Rediscovered letters and postcards highlight the fierce competition among scientists who discovered DNA's famous double-helix structure and unraveled the genetic code. Francis Crick and James D.

For decades, biology textbooks taught that DNA’s story could be told with a single image: two elegant strands twisting in a double helix. That picture is still right, but it is no longer enough.

In geometry a double helix (plural helices) typically consists of two congruent helices with the same axis, differing by a translation along the axis, which may or may not be half-way. The term ...