Is one of a pair of genes that appear at a particular location on a particular chromosome and control the same characteristic. How the characteristic turns out depends on the combination of the 2 alleles. People get one allele from their father and one allele from their mother. For example, alleles control things in people such as the color of their eyes, their blood type, and whether they are colorblind or not.

Refers to any genetically determined characteristic; I.e. Traits are determined by the combination of genes people receive from their parents.

Trait is one that is expressed (shows up) even if it only occurs on one of the two alleles for that trait. A dominant allele is shown by a capital letter. For example, brown eyes are dominant over blue eyes, and are usually depicted as a capital B. Brown eyes, a dominant trait will be seen (expressed) if the alleles are BB or Bb.

Trait requires both alleles to be present in order to be expressed. Blue eyes, for example, are recessive, which means that a blue eyed person has inherited the gene for blue eyes from both their biological parents. In the case of eye color, this would usually be written as bb.

The physical appearance of an organism, or what it looks like and what traits the organism or person has. It is the physical expression of a gene. The phenotype of an organism depends on which genes are dominant and in some cases, on the interaction between genes and the environment of the organism.

The genetic makeup of an organism with reference to a single trait, set of traits, or an entire complex of traits. It is the allele combination for a trait. NOTE: The word genotype is also sometimes used to refer to a group of genetically related organisms.

Refers to having identical pairs of genes (alleles) for any given pair of hereditary characteristics. Traits can be homozygous dominant (BB – brown eyes) or homozygous recessive (bb – blue eyes).

Means having dissimilar pairs of genes (alleles) for any hereditary characteristic. For example, a person will have brown eyes if their genotype is Bb.

Are a method to show and determine allele combinations in one generation (i.e. The offspring of two organisms).