Spacer DNA

Spacer DNA are regions of non-transcribed DNA between tandemly repeated genes, such as ribosomal RNA genes in eukaryotes. Its function most likely involves ensuring the high rates of transcription associated with these genes.

In bacteria, spacer DNA sequences are only a few nucleotides long. In eukaryotes, they can be extensive and include repetitive DNA, comprising the majority of the DNA of the genome. The term is used particularly for the spacer DNA between the many tandemly repeated copies of the ribosomal RNA genes.