Birth Defect Terms and Definitions

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

Hybrid
The offspring of genetically different parents.

Birth defect
Any harmful trait, physical or biochemical, present at birth, whether a result of a genetic mutation or some other nongenetic factor.

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

Mutation
Any heritable change in DNA sequence.

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

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.

Acquired genetic mutation
A change in the genetic structure that is neither inherited nor passed to offspring. Also called acquired mutations.

Autosome
A chromosome not involved in sex determination.

Risk communication
In genetics, a process in which a genetic counselor or other medical professional interprets genetic test results and advises patients of the consequences for them and their offspring.