Threose nucleic acid

Threose nucleic acid (TNA) is a chemical similar to DNA or RNA but differing in the composition of its "backbone". TNA is not known to occur naturally in existing life on Earth.

DNA and RNA have a deoxyribose and ribose sugar backbone, respectively, whereas TNA's backbone is composed of repeating threose units linked by phosphodiester bonds. The threose molecule is easier to assemble than ribose making it a possible precursor to RNA.

DNA-TNA hybrid chains have been made in the laboratory using DNA polymerase.

TNA can specifically base pair with RNA and DNA, this capability and chemical simplicity suggests that TNA could have preceded RNA as genetic material.