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#Sugar phosphate backbone ester code

The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. One of the major differences between DNA and RNA is the sugar, with 2-deoxyribose being replaced by the alternative pentose sugar ribose in RNA. The asymmetric ends of DNA strands are referred to as the 5′ ( five prime) and 3′ ( three prime) ends. This arrangement of DNA strands is called antiparallel. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand. These asymmetric bonds mean a strand of DNA has a direction. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The backbone of the DNA strand is made from alternating phosphate and sugar residues. If multiple nucleotides are linked together, as in DNA, this polymer is referred to as a polynucleotide. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. These two long strands entwine like vines, in the shape of a double helix.

In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules. For instance, the largest human chromosome, chromosome number 1, is 220 million base pairs long. Although each individual repeating unit is very small, DNA polymers can be enormous molecules containing millions of nucleotides. The DNA chain is 22 to 26 Ångströms wide (2.2 to 2.6 nanometres), and one nucleotide unit is 3.3 Ångstroms (0.33 nanometres) long.

1.5 Alternative double-helical structuresĭNA is a long polymer made from repeating units called nucleotides.

Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. These chromosomes are duplicated before cells divide, in a process called DNA replication. Within cells, DNA is organized into structures called chromosomes. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes.

#Sugar phosphate backbone ester code

The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. It is the sequence of these four bases along the backbone that encodes information. Attached to each sugar is one of four types of molecules called bases. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.Ĭhemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate groups joined by ester bonds. DNA is often compared to a set of blueprints, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The main role of DNA molecules is the long-term storage of information. Deoxyribonucleic acid ( DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms.