Cancer may become largely avoidable if we can modify our cells to behave somewhat like those of naked mole rats, for example. That'd require some pretty hefty simulation before it moves out of beta into real human beings (experimentation being unethical, and all that), so may or may not be 'easy' to do in the near to long future. But aging (a diffuse genetic break-down?) may be much harder to solve.
...Comments from hairyears
Everything's got mitochondria, they're made with a fixed amount of deuterium for the service life, and everything is made of stuff that works.
What? Deuterium has nothing to do with mitochondrial function. They're not little fusion reactors, those it's a nice analogy.
Also, not everything has mitochondria, in fact, most organisms lack them (prokaryotes, archaea, some eukaryotes).
]]>...modified ribosomes that can assemble polypeptides using non-standard aminoacids (presumably coded for using four-base codons)...
Biologist here: But that means re-writing every single protein in the genome, completely re-engineering the ribosome (and associated parts of the translation apparatus), a really difficult engineering problem, and probably also dealing with a host of unexpected and difficult-to-fix genetic-control issues (e.g. of genes that are controlled by pseudogene paralogs).
It might be easier to start with engineering some currently synonymous nucleotide triplets to be different, so that they code for new amino acids (the genetic code is partly 'degenerate,' so different triplets currently code for the same amino acid -- some of these synonymous triplets are potentially available as distinct ones for new amino acids).
This still means re-writing much of the current genome (to sort out degeneracy/non-degeneracy issues), though this would be a less radical change than a switch to a quadruplet system.
Making the triplet genetic code less degenerate may cause its own set of long-term problems. Although the current code does vary slightly across organisms, there's good evidence that its level of degeneracy has evolved as an optimal solution to minimize errors in mistranslation and mutation (at least for the current set of amino acids). This may in turn require careful re-optimization of DNA/RNA replication fidelity. There would be many unintended and hard-to-predict consequences like this.
A 4-base code would also be more error prone...
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