Birth Defect Terms and Definitions

Gene
The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product

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

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

Haploid
A single set of chromosomes (half the full set of genetic material) present in the egg and sperm cells of animals and in the egg and pollen cells of plants

Codominance
Situation in which two different alleles for a genetic trait are both expressed.

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.

Phenotype
The physical characteristics of an organism or the presence of a disease that may or may not be genetic.

Cancer
Diseases in which abnormal cells divide and grow unchecked.

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.

Hybrid
The offspring of genetically different parents.