The four nitrogenous bases that make up the DNA structure are divided into two groups, called purines and pyrimidines. Adenine and guanine are purines, and chemically are double-ringed structures - a five cornered ring and a six cornered ring. They are much larger than pyrimidines.
James Mason (I) (1909â1984) James Mason was a great English actor of British and American films. He was born in Yorkshire, and attended Marlborough and Cambridge, where he discovered acting on a lark, and abandoned a planned career as an architect. Following work in stock companies, he joined the Old Vic under the guidance of Sir Tyrone Guthrie and of Alexander Korda, who ...
George Mason in The American Revolution . BACK; NEXT ; George Mason (1725â1792), a Virginian, was one of the most important delegates to the Constitutional Convention, one of the richest men in his state, and one of the most prominent Founding Fathers. In 1759, Mason was elected to the Virginia House of Burgesses and became one of the earliest opponents of British colonial policy.