MUTATA

A book of text, like a genome, is prone to mutations in the editing and copying process. The unintentional mutations spotted in the book by my readers are illustrative. New mutations are gratefully received. They may need their own book.

Deletion and Frame-Shift

In Figure 20.2, (page 204) the photomicrograph, originally called A, was removed to improve the size and clarity of the three chromosome diagrams. The latter were originally labelled B, C and D, and are now A, B and C respectively – a ‘frame-shift’. I altered the caption of the figure to match but did not correct the reference to this in the text on page 203, the first paragraph of which should now read:

“Figure 20.2 is a diagrammatic representation comparing the chromosome banding patterns of humans and chimpanzees. In A each of the 23 chromosomes in a human male is matched with the corresponding chromosome from a chimpanzee male. In B I have enlarged the human chromosome 2 lined up alongside the two chimpanzee chromosomes that correspond to it.”

Because a gene is translated into protein by reading 3-bases as the code for one amino acid, deletions or insertions of bases in multiples of three (3, 6, 9 bases etc) may cause a problem but will leave the ‘words’ in the remainder of the gene ‘understandable’. Deletions (or insertions) of other numbers of bases (1, 2, 4,5,7 etc) will result in a ‘frame-shift’ where all the remaining sets of three bases are dislocated and out of step with the original three-base code. They are very damaging to genes and result in loss of sense in the following part of the gene – they are often called ‘missense mutations’. Many human pseudogenes have become so initially because of deletion+frame-shift mutations – this is part of the problem in the Vitamin C gene called GULO, part of the reason we need Vitamin C in the diet (pages 205-8).

Duplication

The first paragraph of page 220 is duplicated. This arose by accident in the editing process without being specially and deliberately created. Perhaps the word processor misused its ‘widow-control’ function that prevents paragraphs crossing over page-breaks with one line to go, and put a paragraph on both pages (I have seen this happen), after which it was saved and edited with two paragraphs; later editing then pushed those two to the top of a page.

Duplication of genes occurs either during crossing over of chromosomes, or due to the reproduction of jumping genes (or both, as jumping genes can cause mismatching during the crossing over process). It is often followed by point mutations in the second copy, and is the commonest way in which new genetic information is added to the genome. Many websites will tell you that genetic information is only corrupted or deleted, never added, but that is simply not true. Our genomes are filled with thousands of duplicated genes and DNA segments, many of which, like the red opsin gene, and the antibodies our bodes make, add their own function. Brand new duplications are documented frequently in humans, sometimes resulting in disease, sometimes not (see the section on the Opsin Genes, page 237).

Deletion

Page 212 In the shaded box at the bottom “W128X” should read “W1282X”. This is actually a textual mutation of the nickname of a genetic mutation – a kind of mutation in two dimensions. This may herald a new phase of development – orthographico-biologic evolution!

There is a single letter deletion on page 406, reference 147. It should be “Pierre Olivetan’s translation” rather than “transation”. A mis-translation perhaps?