The first use of the term was made to describe a transposition of approximately 7.9 kilobase pairs of the cytoplasmic mtDNA genome into the nucleus of the domestic cat (Felis silvestris catus), where Numt is tandemly repeated, 38-76 times at a single genomic locus on cat chromosome D2.[1] Many Numts are transcriptionally inactive similar to some satellite (or junk) DNA, though they may be considered as part of the Serial Endosymbiosis Theory (SET) or endosymbiotic theory for the origin of eukaryotic cells and organelles.