Describe how long strands of double

Attached to each sugar is one of four bases: adenine A , cytosine C , guanine G , or thymine T. The two strands are held together by bonds between the bases, adenine forming a base pair with thymine, and cytosine forming a base pair with guanine. A double helix has become the icon for many, many kinds of discussions about where science has been and where it's going.

This really is an amazing structure. You can't stare at the double helix for very long without having a sense of awe about the elegance of this information molecule DNA, with its double helical form basically being the way in which all living forms are connected to each other, because they all use this same structure for conveying that information.

Of course, this is Watson and Crick's incredible realization back in , but it will stand in history as probably one of the most significant scientific moments of all time. Francis S. This page has been archived and is no longer updated. The double helix is a description of the molecular shape of a double-stranded DNA molecule. However, a crucial contribution that enabled this discovery was made by Rosalind Franklin, who was not acknowledged at that time.

After her death, Crick said that her contribution had been critical. The double helix describes the appearance of double-stranded DNA, which is composed of two linear strands that run opposite to each other, or anti-parallel, and twist together. Each DNA strand within the double helix is a long, linear molecule made of smaller units called nucleotides that form a chain.

The chemical backbones of the double helix are made up of sugar and phosphate molecules that are connected by chemical bonds, known as sugar-phosphate backbones. The two helical strands are connected through interactions between pairs of nucleotides, also called base pairs.