De Quervain's tenosynovitis is inflammation of tendons on the side of the wrist at the base of the thumb. These tendons include the extensor pollicis brevis and the abductor pollicis longus tendons, which extend the joints of the thumb. De Quervain's tenosynovitis can be brought on by simple strain injury to the extensor pollicis longus and abductor pollicis tendons. Typical causes include stresses such as lifting young children into car seats, lifting heavy grocery bags by the loops, and lifting gardening pots up and into place.
double helix. n. The coiled structure of double-stranded DNA in which strands linked by hydrogen bonds form a spiral configuration, with the two strands oriented in opposite directions.
In 1953 James Watson and Francis Crick published their theory that DNA must be shaped like a double helix. In 1953 James Watson and Francis Crick published their theory that DNA must be shaped like a double helix. A double helix resembles a twisted ladder. Each 'upright' pole of the ladder is formed from a backbone of alternating sugar and phosphate groups. Each DNA base (adenine, cytosine, guanine, thymine) is attached to the backbone and these bases form the rungs. There are ten 'rungs' for each complete twist in the DNA helix.