Nucleotides

There are five different nitrogenous bases that occur in DNA. These are – adenine(A), cytosine(C), guanine(G), thymine(T) and uracil. Uracil is only found in RNA, and thymine can only be found in DNA, one replaces the other. Adenine will only form hydrogen bonds with itself and thymine. Guanine will only bond with cytosine.

There are two types of nitrogen containing nucleotides: Purines: these are made up of a double ring structure consisting of a six and five sided ring, including adenine and guanine. Pyrimidines: are six sided ring structures including thymine, cytosine and uracil. A pyrimidine base will only bond with a purine base.

Nucleotides are the basic building blocks of macromolecules, such as Deoxyribonucleic Acid (DNA), and Ribonucleic Acid (RNA). Nucleotides are built up by a condensation reaction between the three components, (a pentose sugar, a base and a phosphate). The pentose sugar is either ribose, found in RNA, or deoxyribose, found in DNA. Ribose contains one more oxygen atom than deoxyribose.

Two nucleotides join to form a dinucleotide. This is the result of a further condensation reaction between one pentose sugar and the phosphate group attached to another pentose sugar. This process can then be repeated many times to form a polynucleotide molecule, which could contain millions of individual nucleotides. RNA molecules are made up of just one polynucleotide chain, whereas DNA exists as two chains, running in opposite directions and twisted around each other in the form of a double helix.

Polynucleotides are polymers that are made from nucleotides. These nucleotides are joined to each other by condensation. Therefore, every time two nucleotides are joined, a molecule of water is lost. These nucleotides may be joined in any order. Polynucleotides Phosphate Group Water Molecules which are lost. Base Pentose Sugar

End of Show By Vikki Savage, Kerry Acheson and Tara Daze