Note: this glossary was used in our genetics workshops for elementary school teachers. For more information on our workshops, visit our professional development page.

Allele. An alternative form of a gene. E.g. A, B, and O are all different alleles of the bloodtype gene.

Biodiversity. The range of variation among all living organisms. Includes 3 components: genetic diversity, species diversity, and habitat diversity.

Co-dominant. Condition where the phenotypes of both alleles of a particular gene are expressed simultaneously in a heterozygote, e.g. AB bloodtype.

Dominant. The form (allele) of the gene that appears to dominate or mask another form of the gene when two different forms are present, i.e. when the individual is heterogygous (e.g Hh) for that gene. Dominant alleles are often written in capital letters. See recessive.

Gene pool. All the possible alleles for a particular gene (or all genes) within a given population.

Genotype. The composition of alleles of an organism, usually for a few specific genes that are being studied. For example: "A person whose phenotype is type A blood can have a genotype of AA or AO." See phenotype.

Heterozygous. Having two different alleles of a particular gene, e.g. Hh for hairy knuckles or AO for bloodtype. See homozygous.

Homozygous. Having two identical alleles of a particular gene, e.g. HH or hh. See heterozygous.

Phenotype. The observable traits or properties of an organism. Refers to both genetic and non-genetic traits. Often used to refer to a single trait. For example: "My phenotype is hairy knuckles and my genotype is Hh." See genotype.

Population. A local group of individuals belonging to the same species, which are actually or potentially interbreeding.

Punnett Square. A tool used to help predict the results of genetic crosses.

Recessive. The form of the gene that is masked by another form in the heterozygous condition. For example, the allele for no hair on knuckles (h) is recessive to the allele for hairy knuckles (H); a person with Hh genotype has hairy knuckles. Recessive alleles are often written in lower case letters. See dominant.

Trait. Any detectable phenotypic variation of a particular inherited characteristic.

G E N E T I C S Home Page

Genetics Education Networks to Enhance Teaching and Improve Curricula in Science
A Howard Hughes funded Pre-College Science Education Award

Contact mtbrown@u.washington.edu for further information.
last updated 6/21/00