Birth Defect Terms and Definitions

Deletion.
A loss of part of the DNA from a chromosome; can lead to a disease or abnormality.

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

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.

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

Centromere
A specialized chromosome region to which spindle fibers attach during cell division.

Embryonic stem (ES) cells
An embryonic cell that can replicate indefinitely, transform into other types of cells, and serve as a continuous source of new cells.

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

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

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

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