The building blocks of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are molecules called "nucleotides" which are complex in nature. Each nucleotide contain a five carbon sugar, an organic base and a phosphate group. DNA contains 2-deoxyribose sugar molecule and RNA contains ribose molecule. There are five different types of organic bases. They are cytosine, adenine, guanine, uracil and thymine . Each nucleotide contains one of the five organic bases. Guanine, cytosine and adenine are found in both DNA and RNA molecules, whereas thymine is found only in DNA and RNA contains only uracil of these five organic bases. All five of the bases comprises complex ring structure made up of nitrogen and carbon atoms. Due to the presence of nitrogen atoms, the bases are also called as nitrogenous bases. Each of the bases have a different chemical structure. This allows specific base pairing.
DNA is an acronym for Deoxyribonucleic acid. James Watson and Francis Crick were the pioneers who discovered DNA. The presence of DNA in the nucleus of every living cell was discovered by these two pioneers. DNA is a helix double stranded structuremade up of four heterocyclic bases adenine, guanine, cytosine and thymine which are linked together with phosphates and sugar units. One interesting fact is that the even though the proportions of these bases differ in each DNA, the number of adenine is always equal to number to thymine and number of cytosine is always equal to number of guanine. DNA is the source for determining the heredity of a person. It contains the genetic information of an individual and determines the functioning of living beings. It is also very useful in foresic science.
There are two types of organic bases: Purine & Pyrimidine.
Purine Bases: Adenine and guanine constitute purines. Purines are the larger types of bases found in DNA. Two rings of atoms constitute a purine base. Cytosine, thymine and uracil are included in purine base. They have only one ring of the atom. When the bases pair and bond together, the purine bases bond only with the pyrimidine bases. More specifically, adenine bonds only with thymine or uracil and cytosine bonds only with guanine. The DNA molecule is stabilized by the specific base pairing. It is made up of two strands of nucleotides that spiral together to form the shape of a double helix. Adenine and thymine are paired by two hydrogen bonds. Guanine and cytosine are paired by three hydrogen bonds. Only these pairs help in the formation of the required hydrogen bonds that make a DNA stable.
Pyrimidine Bases: It is a single-ringed, crystalline organic base, C4H4N2, that forms uracil, cytosine, or thymine and is the main compound of many drugs, including the barbiturates. Several organic compounds derived from or structurally related to pyrimidine, are the nitrogen bases uracil, cytosine, and thymine.
Guanine combines with cytosine to form a base pair. Guanine binds to cytosine through three hydrogen bonds. The amino group in cytosine acts as the hydrogen donor. C-2 carbonyl and the N-3 amine acts as the hydrogen-bond acceptors. The guanine group at C-6, acts as the hydrogen acceptor and the group at N-1 and the amino group at C-2 is the hydrogen donors.
Guanine has multiple uses. Crystalline guanine is extracted from the scales of some fishes. It is found to have many uses in the cosmetics industry. Crystalline guanine is added in various products like shampoos, where it provides a pearly shimmering effect. It is also used in nail polish and eye shadow to bring shimmering lustre. Facial treatments use the droppings, or guano, from Japanese nightingales. This is currently the flavor in New York, because the guanine in the droppings gives a clear and "bright" skin tone. Crystalline guanine is also used in metallic paints, simulated pearls and plastics.