obsolete genetic dosage [GENO_0000876]

obsolete genetic dosage

ID: GENO_0000876

Genetic dosage reflects how many 'functional' copies of a sequence are present in a genome. In diploid organisms, the normal dosage is 2 for autosomal genes/regions. Dosage increases if there is a duplication of the gene/region. Dosage decreases if there is either a deletion of a gene/region, or an inactivating mutation that eliminates gene function. This sets it apart from the notion of 'copy number', which reflects how many actual copies of a sequence exist in a genome. Addition of a non-functional allele of a gene will increase its copy number, but not increase its dosage. Duplications of a sequence can occur at new locations in the genome, such that the resulting sequence represents a distinct sequence feature from the copy at its native locus. For example, duplication of a region containing the human APOE gene on a different chromosome creates a sequence feature that shares sequence from the original gene, but not location, and therefore represents a different sequence feature. The notions of dosage and copy number are therefore concerned with sequence-level entities (how many copies of a 'sequence' exist), as opposed to sequence feature-level entities. The notion of a single-locus complement would be used to describe how many of a particular features are present in a genome - and describe which alleles of this feature are found.