[Verse 1] Origin fires, helicase splits the ladder wide, Two forks racing outward, one continuous, one denied— Leading strand sprints solo, polymerase glued tight, Lagging strand stutters, Okazaki fragments, primer, bite. Fidelity's the watchword, one error in a billion base, Proofreading domain reads back, kicks the wrong bond off its place, Replication timing marks the early and the late, Heterochromatin dozes while the euchromatin can't wait. [Chorus] Mismatch, base, nucleotide — three repair crews on patrol, Cut the wound, fill the gap, ligase seals the scroll, HR borrows a sister, NHEJ just glues the ends, Watch the fork, guard the code, that's how the genome defends. [Verse 2] Mismatch repair spots the loop the polymerase missed, Base excision plucks a damaged letter off the list, Nucleotide excision cuts a patch when UV bends the strand, Double-strand breaks call for backup, pick a repair band— Homologous recombination's careful, copies from a template true, NHEJ's the reckless medic, stitching blunt ends fast, askew, MMEJ's the shortcut cousin, microhomology as its guide, Every choice in that decision shapes what mutations will hide. [Verse 3] Meiosis shuffles chromosomes, crossovers cut and swap, PRDM9 marks the hotspots where the recombining won't stop, Gene conversion copies one allele to overwrite the other— Non-reciprocal theft between a chromosome and its brother. Transitions keep it in the family, purine to purine stays, Transversions cross the aisle, purine turns to pyrimidine ways, Indels slip like loose scaffolding, MNVs travel in a pack, Aneuploidy's the whole chromosome that never got sent back. [Bridge] CpG's a hot seat, methylate then deaminate to T, Every cancer genome's a palimpsest — old scratches under new debris, Layers of signatures written, erased, rewritten again, Somatic in the tumor, germline passed to kin, Mosaic cells whisper different codes beneath one skin, Clonal hematopoiesis — blood's rebellion from within. [Verse 4] Count your transitions, count your transversions, divide and you'll see— Two-point-oh to two-point-one is the genome's steady decree, Exomes climb to three 'cause CpG islands hide in exons tight, Build the ninety-six-channel spectrum, trinucleotide left and right, Simulate the SNVs, dial the Ti/Tv rate you need, Elevate the CpG channel, watch the signature succeed, Decompose it with least squares, match it to the known, Every mutation's a fingerprint — the cell's confession, carved in stone. [Chorus] Mismatch, base, nucleotide — three repair crews on patrol, Cut the wound, fill the gap, ligase seals the scroll, HR borrows a sister, NHEJ just glues the ends, Watch the fork, guard the code, that's how the genome defends. [Outro] Fork to fix, break to bind, every base earns its stripe, Read the spectrum, trust the ratio, decode the genotype.
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