| Term | Definition |
| pedigree | a diagram that traces the inheritance of a particular trait through several generations |
| circles | represent females on a pedigree |
| square | represent males on a pedigree |
| half-filled circle/square | shows a person is a carrier for a disease on a pedigree |
| filled in circle/square | shows a person has a disease on a pedigree |
| multiple alleles | a form of inheritance which is determined by more than the regular two alleles (example-blood type) |
| epistasis | the result of the interaction of 2 genes, each with 2 alleles where one allele hides the effect of another allele creating variety (example-labrador retrievers) |
| XY | sex chromosomes of a male |
| XX | sex chromosomes of a female |
| autosomes | regular body chromosomes that code for everything except the sex |
| Barr body | an inactivated turned off X chromosome in the nuclei of a cell |
| sex-linked traits | traits controlled by genes on the X chromosome (example-hemophilia or ALD) |
| nondisjunction | during cell division the sister chromatids fail to separate correctly |
| albinism | disorder that results in absence of the skin pigment melanin in the hair and eyes |
| Tay-Sachs disease | results in a cherry red spot on the back of the eye and inflated nerve cells which cause retardation |
| Huntington's disease | results in a gradual loss of brain function, uncontrollable movements and emotional disturbances |
| cystic fibrosis | characterized by secretions of thick mucus that affect pancreas, digestion and respiratory pathways in lungs |
| galactosemia | inability to break down galactose |
| achondroplasia | results in dwarfism with short limbs and a small body size |