My wife, a school psychologist by trade, became fascinated with the modern theory of evolution as expounded by Richard Dawkins in his book The Selfish Gene . The book, that she finished reading in March, afforded us in April a series of interesting family discussions. Among laymen and philosophers, Dawkins is famous for raising the issue of cultural evolution brought about with the emergence of memes , the new kind of replicators. Compared to the Darwinian evolution, cultural evolution is orders of magnitude faster. Natural evolution is about replication and propagation of genes.
Genes live on chromosomes, chromosomes live in cells.
In usual cells, chromosomes live in pairs. In the sex cells, the sperms and eggs, chromosomes come in singles. When two sex cells fuse into one, the newly formed cell receives 1 chromosome from each of the parent cells. Not unexpectedly, most of the fun occurs in production of sex cells each of which carries single chromosomes. The paired genes are known as alleles of each other.