The sequence of nucleotide pairs in the DNA determines all of the hereditary characteristics of any given organism. The Z form can exist in DNA sequences with alternating guanine and cytosine bases and may be functional in localized DNA regions however, the B form is thought to predominate in most biological systems. One configuration, termed the Z form, is a left-handed helical structure. In addition, DNA can exist in helical structures other than the B form.

In the Watson-Crick model, the two opposing DNA strands have an opposite polarity that is, they are antiparallel, with their 5′ ends lying at opposite ends of each double-stranded molecule. Each of the base pairs lies in a plane at approximately right angles to the helix axis, forming a stack with the two sugar-phosphate chains coiled around the outside of the stack. The configuration of the bases allows hydrogen bonding between opposing purines and pyrimidines. The strands wind about each other, with their sugar-phosphate chains forming the coil of the helix and with their bases extending inward toward the axis of the helix.

In most DNAs, there are two single DNA strands that compose each helix. See also: Cell (biology) Deoxyribonucleic acid (DNA) Molecular biology Purine Pyrimidine Ribonucleic acid (RNA)ĭNA can assume a structure called the B form, which is a right-handed helical configuration resembling a coiled spring. There are two types of nucleic acids-deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). 1) are collectively involved in the preservation, replication, and expression of hereditary information in every living cell.

The primary biological role of RNA is to direct the process of protein synthesis.Īn acidic, chainlike biological macromolecule consisting of multiple repeated units of phosphoric acid, sugar, and purine and pyrimidine bases. Information is contained in the DNA in the form of the sequence of nucleotide building blocks in the nucleic acid chain. There are two types of nucleic acids-deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).ĭNA is the chemical constituent of the genes of an organism. Nucleic acids are involved in the preservation, replication, and expression of hereditary information in every living cell. A nucleic acid is an acidic, chainlike biological macromolecule consisting of multiple repeated units of phosphoric acid, sugar, and purine and pyrimidine bases.

Download nucleic acid structure