DNA
The genetic material in the nucleus of a cell is composed of a chemical called DNADeoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being.. DNA is a polymer - a large and complex molecule, made from many small monomerSmall molecule, usually containing a C=C bond, that can join end to end with other monomers to form a polymer molecule. It is made up of two strands forming a twisted ladder structure called a double helixThe shape of the DNA molecule, with two strands twisted together in a spiral.. It carries the genetic codeThe code formed by the order of the bases in DNA that determines an organism's characteristics., which determines the characteristics of a living organismLiving entity, eg animals, plants or microorganisms..
Except for identical twins, each person's DNA is unique. This is why people can be identified using DNA fingerprinting. DNA can be cut up and separated, which can form a 'bar code' that is different from one person to the next.
Chromosomes
The cell's nucleusThe nucleus controls what happens inside the cell. Chromosomes are structures found in the nucleus of most cells. The plural of nucleus is nuclei. contains chromosomeThe structure made of DNA that codes for all the characteristics of an organism.. These are long threads of DNA, which are made up of many genes.
Genes
A gene is a small section of DNA in a chromosome. Each gene codes for a particular sequence of amino acids in order to make a specific protein. A gene is the unit of heredityGenetic information that determines an organism's characteristics, passed on from one generation to another. To do with passing genes to an offspring from its parent or parents., and may be copied and passed on to the next generation.
DNA base pairs
The basic units (monomers) of DNA are nucleotides. These nucleotides consist of a deoxyribose sugar, phosphate and base. The nucleotides are identical except for the base, which can be an adenine (A), thymine (T), guanine (G) or cytosine (C).
Bases are complementary. This means they always pair in the same way: A with T, T with A, C with G and G with C.
These basic units are linked together to form strands by strong covalent bonds between the deoxyribose sugar of one nucleotideThe units or molecules of which DNA is composed. and the phosphate of the next nucleotide. These strong bonds form a sugar-phosphate backbone.