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Chemical structure of DNA; hydrogen bonds shown as dotted lines. Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3′ hydroxyl group (—OH) on the other. DNA is a long polymer made from repeating units called nucleotides.
DNA encodes information through the order, or sequence, of the nucleotides along each strand. Each base—A, C, T, or G—can be considered as a letter in a four-letter alphabet that spells out biological messages in the chemical structure of the DNA.
DNA, organic chemical of complex molecular structure found in all prokaryotic and eukaryotic cells. It codes genetic information for the transmission of inherited traits. The structure of DNA was described in 1953, leading to further understanding of DNA replication and hereditary control of cellular activities.
The DNA molecule is a polymer of nucleotides. Each nucleotide is composed of a nitrogenous base, a five-carbon sugar (deoxyribose), and a phosphate group. There are four nitrogenous bases in DNA, two …
DNA (deoxyribonucleic acid) molecules are nucleic acids, which are the information-carrying molecules of the cell. DNA molecules are polymers and are made up of many smaller molecules, called nucleotides. Each nucleotide contains a phosphate group, a sugar molecule, and a nitrogenous base.
The sequence of nucleotides that make up a molecule of DNA is referred to as its primary structure. A DNA molecule consists of two chains of polymerized nucleotides running side-by-side, joined together by hydrogen bonds forming between their nitrogenous bases (Figure 2a).
DNA stands for Deoxyribonucleic acid, a macromolecule that carries genetic information in all living organisms, from the tiniest microorganisms to the most complex multicellular humans. DNA is a fundamental molecule that holds life’s blueprint.
DNA Structure. Watson and Crick proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. The two DNA strands are antiparallel, such that the 3ʹ end of one strand faces the 5ʹ end of the other (Figure \(\PageIndex{6}\)).
DNA is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope. The entire genetic content of a cell is known as its genome, and the study of genomes is genomics.
In this chapter we begin by describing the structure of DNA. We see how, despite its chemical simplicity, the structure and chemical properties of DNA make it ideally suited as the raw material of genes.