Glossary

• Cell: The smallest functioning unit of a living organism that works independently.
• DNA (deoxyribonucleic acid): A double helix made of nucleotides, found in the nucleus of eukaryotic cells; the molecule that determines the genetic characteristics of most living things.
• Nucleotide: The building blocks of DNA; comprised of deoxyribose sugar, a phosphate group, and a nitrogen-rich base.
• Chromosome: Thread-like structures in the nucleus; comprised of DNA and proteins; contains the genetic information in the form of genes.
• Gene: A section of DNA that carries the genetic code for a particular characteristic.
• Complementary base pairing: A pair of bases that can join together to make the rungs of the DNA ladder - adenine and thymine (A 2 T), guanine and cytosine (G 3 C).
• Homologous chromosomes: Chromosomes with genes for particular characteristics at the same location.
• Somatic: Body cells.
• Gamete: Sperm and egg (sex) cells.
• Diploid: The number of chromosomes in body cells; two sets or 2n. In humans 2n = 46.
• Haploid: The number of chromosomes in gametes; one set or n. In humans n = 23.
• Autosome: All chromosomes in a cell other than the sex chromosomes.
• Sex chromosomes: The chromosomes that determine the sex of an individual; in humans they are X and Y.
• Zygote: The cell formed by the fusion of two gametes, a sperm and an egg.
• Blastocyst: Ball of cells that forms early in a pregnancy, about 5-7 days after a sperm fertilises an egg.