The level of occurrence of a single DNA Sequence Variation within a set of chromosomes. Heterozygous indicates the DNA Sequence Variation is only present in one of the two genes contained in homologous chromosomes. Homozygous indicates the DNA Sequence Variation is present in both genes contained in homologous chromosomes. Hemizygous indicates the DNA Sequence Variation exists in the only single copy of a gene in a non- homologous chromosome (the male X and Y chromosome are non-homologous). Hemiplasmic indicates that the DNA Sequence Variation is present in some but not all of the copies of mitochondrial DNA. Homoplasmic indicates that the DNA Sequence Variation is present in all of the copies of mitochondrial DNA. Here is the loinc answer List for Allelic state:1. Heteroplasmic (LA6703-8); 2. Homoplasmic (LA6704-6); 3. Homozygous (LA6705-3); 4. Heterozygous (LA6706-1); 5. Hemizygous (LA6707-9).

unique id for the element within a resource (for internal references).

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition should be version specific. This will ideally be the URI for the Resource Profile defining the extension, with the code for the extension after a #.

Value of extension - may be a resource or one of a constrained set of the data types (see Extensibility in the spec for list).