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dbSNP:

NCBI database of genetic variation. https://www.ncbi.nlm.nih.gov/snp/

Deletion (del):

The loss of genetic material, ranging from a single nucleotide to an entire chromosome.

De novo mutation:

A genetic alteration which arises in an individual that was not inherited from a parent, or was present for the first time in the egg or sperm from the parent.

Depth of coverage (depth):

The number of sequencing reads generated during massively parallel sequencing which align to and cover a specific genomic region or base pair. Higher depth of coverage generally increases confidence in variant calls.

Dizygotic twins (DZ):

Twins that developed from two separate fertilized eggs (fraternal twins).

DNA:

Deoxyribonucleic acid

Dominant:

A characteristic, trait, or disorder which is phenotypically expressed when only one variant allele is present.

Dominant negative:

A mutation which results in an altered protein which interferes with the normal wild-type protein product, and may result in a novel protein function. These types of mutations may be more deleterious than a mutation which results in a premature stop or null allele when polymeric molecules are involved.

Double heterozygote:

When an individual is heterozygous at two different loci (which results in a disease).

Duplication (dup):

An additional copy (gain) of genetic material, ranging from a single nucleotide to an entire chromosome.

DZ:

See dizygotic twins.