Notable Quotes Two

A portrait of Ohno
Susumu Ohno
The points I wish to make are:

1) Natural selection is an extremely conservative force. So long as a particular function is assigned to a single gene locus in the genome, natural selection only permits trivial mutations of that locus to accompany evolution.

2) Only a redundant copy of a gene can escape from natural selection and while being ignored by natural selection can accumulate meaningful mutation to emerge as a new gene locus with a new function. Thus, evolution has been heavily dependent upon the mechanism of gene duplication.

3) The probability of a redundant copy of an old gene emerging as a new gene, however, is quite small. The more likely fate of a base sequence which is not policed by natural selection is to become degenerate. My estimate is that for every new gene locus created about 10 redundant copies must join the ranks of functionless DNA base sequence.

4) As a consequence, the mammalian genome is loaded with functionless DNA.

Ohno, Susumu. 1973. Evolutional reason for having so much junk DNA. In Modern Aspects of Cytogenetics: Constitutive Heterochromatin in Man (ed. R.A. Pfeiffer), pp. 169-173. F.K. Schattauer Verlag, Stuttgart, Germany.

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