It has been 50 years since scientists first created DNA in a test tube, stitching ordinary chemical ingredients together to make life's most extraordinary molecule. Until recently, however, even the most sophisticated laboratories could make only small snippets of DNA -- an extra gene or two to be inserted into corn plants, for example, to help the plants ward off insects or tolerate drought.

Now researchers are poised to cross a dramatic barrier: the creation of life forms driven by completely artificial DNA.

Scientists in Maryland have already built the world's first entirely handcrafted chromosome -- a large looping strand of DNA made from scratch in a laboratory, containing all the instructions a microbe needs to live and reproduce.

A variant in a gene encoding a key regulator of the immune system increases the risk of multiple sclerosis, report two papers to be published online this week in Nature Genetics. Multiple sclerosis is a chronic and debilitating autoimmune disease in which neurons of the central nervous system become demyelinated, resulting in progressive neurodegeneration.