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Base Chemical Components of DNA

DNA polymer The Polymer

DNA is a very long and intricate macromolecule. The term macro refers to the fact that it is a molecular structure made up of many smaller molecules themselves. Following is a 'brief' synopsis of the various chemical/molecular components of the DNA macromolecule itself.

First of all, DNA is a type of nucleic acid. Basically, a nucleic acid is a macromolecule composed of several chains of smaller monomers named nucleotides. Biologically speaking, the role of any nucleotide is to carry genetic information, or to form structures within the cell itself. Although DNA (and its cousin RNA) are the most common nucleic acids, there are also others, including many known synthesized nucleic acids.

DNA's main molecular component (albeit not necessarily the component which defines its genetic sequencing) is the two long polymer strands with made up the sides of the molecule. The polymers themselves are large, macromolecules consisting of repeated structural units connected chemically. Although there are many different forms of polymers, both natural (biological) and synthetic (man made).

The DNA polymer is a chemical construction made primarily out a sugar called deoxyribose. This sugar is connected through a repeating architecture by a chemical connection known as a phosphodiester bond (illustrated below). This bond is known as such because it consists of a linkage between two deoxyribose molecules made by a phosphorous atom in a phosphate group over two 'ester' bonds (hence the name phospho- [after phosphorous] di- [after two] and ester [after the type of connection being made]).

The Bases

Although not the largest part structurally, the organization of the 'base' components of the DNA macromolecule are determinative of what actually gives the molecule its genetic determinative qualities. There are four different chemical bases in DNA, known as adenine, cytosine, guanine and thymine (abbreviated A, C, G, T) These bases combine chemically with the phosphate-deoxyribose polymers of the DNA molecule in a structural arrangement which provides DNA with its functional qualities. The actually bond itself between the base molecule and the polymer is made on the deoxyribose (sugar) molecule, and not on the phosphate connection.

The bases themselves are arranged in pairs, with adenine and thymine being paired together, as well as cytosine and guanine being paired together. Basically, if one polymer strand has an adenine base attached to a deoxyribose unit, then the complimentary or conjoining polymer will undoubtedly have a thymine attached to a deoxyribose unit in the same location. Conversely, supposing a guanine base is attached to the polymer in a specific location, then the complimentary location on the conjoining polymer will be connected to a cytosine base.

DNA base molecules

The bases themselves attach to each other, essentially 'holding' the two polymers together with hydrogen bonds. The hydrogen bond is very simple (chemically speaking) and easily allows for the dissociation of the polymer strands during the chemical seperation required during replication.

The bases, also known (chemically) as 'nucelobases' are technically referred to as 'heterocyclic aromatic organic compounds', where heterocyclic refers to the shape of the molecule, aromatic to the type bond in question and organic to the fact that it contains carbon, hydrogen and oxygen. The 'nucleobase' molecules also contain nitrogen atoms as well.

As previously mentioned, the bases are complimentary in nature, suggesting the manner in which they must be paired up in the structural chain. Pairing always occurs in the form C-G or A-T, where a purine (either adenine or guanine) is always paired with a pyrimidine (either cytosine or thymine).

DNA Base Attachments

Chemical Components

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