Birth Defect Terms and Definitions

Single-gene disorder
Hereditary disorder caused by a mutant allele of a single gene.

Hybrid
The offspring of genetically different parents.

Junk DNA
Stretches of DNA that do not code for genes; most of the genome consists of so-called junk DNA which may have regulatory and other functions.

Syndrome
The group or recognizable pattern of symptoms or abnormalities that indicate a particular trait or disease.

Amino acid
Any of a class of 20 molecules that are combined to form proteins in living things.

Cancer
Diseases in which abnormal cells divide and grow unchecked.

Pedigree
A family tree diagram that shows how a particular genetic trait or disease has been inherited.

Fraternal twin
Siblings born at the same time as the result of fertilization of two ova by two sperm. They share the same genetic relationship to each other as any other siblings.

Identical twin
Twins produced by the division of a single zygote; both have identical genotypes.

Mitosis
The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell.