Probability - The chance or possibility that a specific event will occur.

Cross - Mating of two organisms.

Offspring - Results of a cross; "young" produced by cross.

Gene - Section of a chromosome that carries the information for a specific trait.

Allele - Alternate forms of a gene.

Chromosomes - Threadlike strand found in the nucleus made up of a series of genes; carries genetic information, DNA.

Dominant - Gene/trait that appears or expresses itself; shown with a capital letter (e.g. Tall = T, Brown = B, etc.).

Recessive - Gene/trait that is hidden in the presence of a dominant; shown with a small, or lower-case, letter (e.g. short = t, blue = b, etc.).

Genotype - Genetic makeup of an organism (e.g. TT, Tt, tt).

Phenotype- Physical appearance of an organism (e.g. tall, short). Usually the appearance of the dominant gene, or the recessive if it is a purebred trait.

Hybrid - Organism with different alleles/genes for a trait (see heterozygous) .

Purebred - Organism with identical alleles/genes for a trait (see homozygous).

Sex chromosomes - The chromosomes that determine the sex or gender of an organism. An organism with two X chromosomes (XX) is a female. An organism with one X chromosome and one Y chromosome (XY) is a male.