<unk>  (TAGs) are a<unk> cluster created by tandem duplications, a process in which one<unk> is duplicated and the copy is found adjacent to the original. They serve to encode large numbers of<unk>  at a time. TAGs represent a large proportion of<unk>  in a genome, including between 14% to 17% of the human, mouse, and rat genomes. TAG clusters may have as few as two<unk> , with small clusters predominating, but may consist of hundreds of<unk> . An example are tandem clusters of rRNA encoding<unk> . These<unk>  are transcribed faster than they would be if only a single copy of the<unk> was available. Additionally, a single RNA<unk> may not be able to provide enough RNA, but tandem repeats of the<unk> allow sufficient RNA to be produced. For example, cells in a human embryo contain between five and ten million ribosomes, and cell number doubles within 24 hours. In order to provide the necessary ribosomes, multiple RNA polymerases must consecutively transcribe multiple rRNA<unk> . In some species, such as Arabidopsis thaliana and Oryza sativa, most TAGs are the result of unequal chromosomal crossover during<unk> ic recombination.
Tandemly arrayed genes
Chimeric gene
Active chromatin sequence
Low copy repeats
Fusion transcript
Fusion gene
Oncogenic retroviridae protein
Insertion sequence