📝 checkpoint_genetics_origin_of_life.mdTheme:

Checkpoint: genetics and origin of life, 12 November 2026

Settled in this thread

The ribosome's catalytic core is RNA, so it can't be the whole origin story. It is the machine that made peptide-RNA pairing precise. It doesn't copy RNA.
Double-stranded RNA appears only in viruses as a genome. Cells use it briefly or as a defence signal. Triple strands exist only as short functional stretches.
Amino acids can't become bases alone, because they carry one nitrogen and adenine carries five. Hydrogen cyanide chemistry (Oró) is the rival nitrogen route.
Methane was probably patchy on early Earth, not dominant. It isn't the nitrogen source, but it is the carbon that can combine with N₂ to form hydrogen cyanide.
The bases' unique feature is selective hydrogen-bond pairing, supported by constant pair width, stable forms and ultraviolet resistance.
Thymine is 5-methyluracil (uracil is the plain one). DNA uses thymine so deaminated cytosine shows up as damage. Cells make it by methylating dUMP, never by converting RNA's uracil in place.
Ribothymidine in tRNA is a hybrid, not a bridge, since it is made by a separate route. The real bridge is ribonucleotide reductase.
Corrections to earlier ideas: methyl hydrogens are not reactive, ribose is the fragile sugar (deoxyribose is stable), and esters are a bond type and not sugar derivatives.

A nucleic acid is a fixed acid that can't turn into a base, with ribose and deoxyribose as neutral spacers.
Nitrogen is needed to turn amino acids into bases, and bases attached to nucleic acid only after the prion formed.

"Ribose holds the information": the backbone is identical along the strand, so it can't carry sequence. Needs a mechanism or a rewrite.

Wet-dry test: ribose plus bases with and without amyloid peptides.
Lipids and peptide-nucleotide joining.
Family-tree comparison of ribonucleotide reductase, the two thymidylate synthases and tRNA-loading enzymes.
Write the model as numbered steps, with what would prove each one wrong.