FAFLife on Earth is based on nucleic acids that contain ribose (RNA) or deoxyribose (DNA) sugar moieties. However these are not the only polymers able to contain and transmit genetic information. It has been observed recently that, with the appropriated polymerases, nucleic acids based on other kind of sugars (such as arabinoses) can replicate.
So, why does nature use riboses? We do not know.
To help solve this problem, scientists from IQFR and McGill University in Montreal, funded by a CSIC I-link Project, have determined the structure of the “arabino nucleic acid” that it turned out to be very similar to our DNA.
Similar, but not identical. And the differences may be important, since they affect the stability of the double helix and other alternative structures. In addition, arabino-oligonucleotides and their fluoro-derivatives have very promising applications in biomedicine. In particular, they could prove very useful as they are resistant to ribonucleases, the enzymes which normally cleave and recycle nucleic acids, which in Earth have evolved to cleave nucleic acids based on ribose, but not in arabinose.
Referencia: The solution structure of double helical arabino nucleic acids (ANA and 2'F-ANA): effect of arabinoses in duplex-hairpin interconversion
Nerea Martin-Pintado et al., Nucleic Acids Res, 2012; doi: 10.1093/nar/gks672