- Allele: "One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome."
- Gene: "A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring"
- Dominant: "An allele that is fully expressed in the phenotype of a heterozygote"
- Recessive: "A genetic trait that lacks the ability to manifest itself when a dominant gene is present"
- Homozygous: "An organism that has a pair of identical alleles for a trait"
- Heterozygous: "An organism that has two different alleles for a trait"
- Punnett Square: "The Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment. It is named after Reginald C.Punnett, who devised the approach, and is used by biologists to determine the probability of an offspring's having a particular genotype."
- Monohybrid: "A cross between two organisms that differ with respect to a single trait."
- Dihybrid: "A cross between two organisms that are each heterozygous for two traits of interest."
- Mendel: "(1822–1884) Austrian scientist and monk who is considered the founder of the science of genetics. His quantitative analysis of the inheritance of certain traits in pea plants allowed him to deduce two fundamental principles known as the laws of Mendelian"
- Incomplete Dominance: "A form of inheritance in which the phenotype of a heterozygote is intermediate between the phenotypes of individuals who are homozygous for each allele."
- Co-dominance: "A version of a gene that is co-expressed with another allele in the heterozygote."
- Sex-linked: "Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance."
- Independent Assortment: "One of Mendel’s laws that states each pair of alleles segregates independently of one another during the formation of gametes."
- Law of Segregation: "One of Mendel’s laws that states that two copies of a gene will segregate so that each gamete receives only one copy."
- Genotype: "The genetic code passed down from parents to offspring that determines all physical and physiological traits, also called phenotypes."
- Phenotype: "The observable traits of an individual, which are passed on from parent to offspring."