Alternative biochemistry

Alternative biochemistry is the study of possible biological chemistries that differ from Earth’s familiar DNA-, protein-, and water-based systems. It explores how life might store information, catalyze reactions, and use solvents with different molecules.

Nucleic acid analogue: A molecule proposed to store and transmit genetic information in place of DNA or RNA. Alternative genetic polymers could preserve heredity while using different backbones or bases.
Astrobiology: The study of life’s origin, evolution, distribution, and future in the universe. Alternative biochemistry helps define what extraterrestrial life might look like beyond familiar terrestrial signatures.
DNA: A nucleic acid that stores hereditary information in most known organisms. It is the familiar genetic system that alternative information polymers would replace.
Origin of life: The set of processes by which nonliving chemistry gave rise to the first living systems. Alternative chemistries broaden the possible routes from planetary chemistry to life.
Definition of life: A set of criteria used to distinguish living systems from nonliving matter. Alternative chemistries test whether standard definitions depend too heavily on terrestrial examples.
Xeno nucleic acid: A synthetic genetic polymer whose backbone differs from the ribose-phosphate backbone of DNA and RNA. Xeno nucleic acids test whether heredity requires Earth’s standard sugar-phosphate structure.
Titan (moon): Saturn’s largest moon, with a nitrogen-rich atmosphere, hydrocarbon lakes, and a surface far colder than Earth’s. Its methane and ethane lakes motivate questions about life using non-water solvents.
RNA: A nucleic acid involved in gene expression, regulation, and catalysis in known life. RNA combines information storage and catalytic roles that hypothetical systems may distribute differently.
Prebiotic chemistry: Chemical reactions that can occur before life exists and may contribute to its emergence. It can reveal whether proposed alternative building blocks form naturally in planetary environments.
Rare Earth hypothesis: The hypothesis that complex life is uncommon because Earth-like conditions are rare. Alternative biochemistry could expand the range of environments capable of supporting life.

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