The Selfish Gene: 40th Anniversary edition (Oxford Landmark Science) — 3. Immortal Coils

1. 1. All organisms, from bacteria to elephants, are survival machines built by the same kind of replicator: DNA molecules.
2. 2. The original replicators may have been inorganic crystals, not organic molecules, as suggested by A. G. Cairns-Smith.
3. 3. A gene is defined as a portion of chromosomal material that potentially lasts long enough to serve as a unit of natural selection.
4. 4. Crossing-over during meiosis shuffles genes, making individual chromosomes temporary while genes themselves can be near-immortal.
5. 5. Genes are selfish in the sense that they compete directly with their alleles for survival in the gene pool.
6. 6. Senile decay is a by-product of late-acting lethal genes that accumulate in the gene pool because they only harm the body after reproduction.
7. 7. The existence of sex and crossing-over is explained from the selfish gene's perspective: genes for sex manipulate other genes for their own propagation.
8. 8. Surplus DNA that does not code for proteins may be parasitic or harmless passengers hitchhiking in survival machines.