A few sorts of chemicals, natural and man made, cause point mutations by interacting with the bases that make up DNA. Some of these substances, such as zinc and fat, are needed by cells for proper functioning. Under certain rare circumstances, even water causes point mutations. Needless to say, all living things suffer point mutations from chemicals once in a while. (In real life, the study of chemical mutagens is a large field. Those interested in the details should see the bibliography).

A small class of chemicals can cause frame shift mutations by inserting themselves between the bases that make up an Instruction. This changes the way the the bases are grouped into codons. This in turn changes how the Instruction is turned into a worker, usually producing one that doesn't do anything. To see how this works, let's pretend that all words contain only three letters, like codons do. We could then make up an Instruction like "Get the fat cat off the big red hat." If we insert an "r" into "cat", we change the Instruction to read: "Get the fat car tof fth ebi gre dha.". (The final "t" is lost because it doesn't form a three letter word.) Not only is the Instruction reduced to gibberish part-way through, the part that makes sense and could be acted on now has a very different specificity: it gets fat cars rather than fat cats! Once in a long while, frameshifts also occur due to errors in copying Instruction Books during asexual reproduction.

Most living things more frequently encounter another kind of radiation: ultraviolet light (UV light). UV light can chemically alter adjacent AA, TT, and TA bases in DNA. This bit of molecular origami changes the shape of the DNA double helix so much that it can neither be expressed nor copied. While organisms have a repair system that undoes this mutation, it's often slow, so living things have a back-up system that allows them to copy the affected Instruction by inserting a pair of bases randomly into the new DNA strand instead of the complements of the ones that can't be read. This causes a point mutation in the new Instruction.

As with point mutations, these other kinds of mutations are always passed on to the offspring of unicellular organisms, but affect the offspring of multicellular organisms only if they occur in their germ line.

Since organisms can't avoid things that change their Instruction Books, they have evolved elaborate systems for repairing or coping with changes. All living things have repair workers that fix point mutations, whether caused by mistakes in copying their Instruction Book, by chemicals, or by radiation. So long as these workers can keep up with the rate of point mutations and fix them all before the Book is copied, the Instruction Book the organism gives to its children is identical to its own. Usually, though, the repair workers fall a little behind, and a few changes sneak into the Book.

Since frame-shift mutations and nonsense mutations can completely ruin an Instruction, living things have tricks for surviving even if such a mutation caused them to inherit garbled Instructions. To cope with frameshifts, organisms will very rarely try to translate four bases of the genetic code into a single link of protein. Although this usually produces useless, frameshifted translations of perfectly good genes, it allows organisms to survive if an important Instruction has been frameshifted. Similarly, once in a while, a living thing will ignore the stop codon at the end of an Instruction and continue to translate it into protein until it reaches the next stop codon. While this usually needlessly sticks extra links onto the ends of workers, this trick permits the organism get by despite the damage to an Instruction.

Finally, many living things keep multiple copies of some Instructions in their Instruction Books. For example, almost all organisms have several copies of the workers that translate Instructions into workers. Even if a mutation were to destroy or garble one of these vital Instructions, the organism can continue using the other copies. Most organisms keep these "back up" copies of important Instructions. Since eukaryotes already have two copies of each Instruction, they already have all their Instructions copied, although the two copies may be different. As an additional safeguard, eukaryotes sometimes duplicate critical Instructions, ending up with four copies, two in each Instruction Book.