Glossary: mode of inheritance

Individuals in a pedigree who exhibit the specific phenotype under study.

Refers to any of the chromosomes numbered 1-22 or the genes on chromosomes 1-22. This term excludes the sex-determining chromosomes, X and Y.

Autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene (i.e., the person is homozygous for a mutation, or carries two different mutations of the same gene, a state referred to as compound heterozygosity).

In medicine, a disturbance of normal functioning of the mind or body. Disorders may be caused by genetic factors, disease, or trauma.

Inherited; having to do with information that is passed from parents to offspring through genes in sperm and egg cells.

The manner in which a genetic trait or disorder is passed from one generation to the next. Autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, multifactorial, and mitochondrial inheritance are examples. Each mode of inheritance results in a characteristic pattern of affected and unaffected family members.

An individual who does not manifest symptoms of a condition or disease occurring in his or her family.

X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, will be unaffected.