DNA, genes and chromosomes


DNA molecules are large and complex. They carry the genetic code that determines the characteristics of a living organism.

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, forming a sort of 'bar code' that is different from one person to the next.


A gene is a section of DNA that codes for a specific protein. It is the unit of heredity, and may be copied and passed on to the next generation.


The cell’s nucleus contains chromosomes. These are long threads of DNA, each made up of many genes.

The diagram shows the relationship between the cell, its nucleus, chromosomes in the nucleus, and genes.

Nucleus, with a chromosome magnified showing the DNA of a gene.
  1. chromosome The structure made of DNA that codes for all the characteristics of an organism.
  2. diploid A cell that contains two sets of chromosomes.
  3. DNA Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being.
  4. double helix The shape of the DNA molecule with two strands twisted together in a spiral.
  5. gamete Sex cell (sperm in males and ova/eggs in females).
  6. gene The basic units of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production.
  7. haploid A sex cell (gamete) that contains one set of chromosomes.
  8. heredity Genetic 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.
  9. mitosis A type of cell division which produces daughter cells identical to the parent.
  10. nucleus The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.
  11. organism Living entity, eg animals, plants or microorganisms.