Mutation

Abstract

Anatomical or physiological variations that are inherited are due to inherited changes (mutations) in base sequences of DNA. Mutations that change genes can affect the conventional phenotype resulting in linear within-species evolution, often under the influence of natural selection (species survival). These changes associate with amino-acid-changing (non-synonymous) mutations in the first or second bases of triplet codons. DNA mutations can also result in changes in the genome phenotype. These changes associate with synonymous (non-amino-acid-changing) mutations, usually in the third bases of codons. Each gene in a genome has distinctive rates of acceptance of amino-acid-changing and synonymous mutations, which are positively correlated. A gene with few amino-acid-changing mutations also has few synonymous mutations. A gene with many amino-acid-changing mutations also has many synonymous mutations. Two genes may be closely located but differ greatly in their mutation acceptance rates. Thus, each gene is an independent mutational entity. Synonymous mutations, and correlated mutations in regions that do not encode amino acids, may be important for changing the ‘pattern’ of a genome, so sparking the onset of branching evolution (species arrival). By eliminating redundant information, oligonucleotide frequency patterns should provide rapid and more sensitive indices of species differences than direct sequence comparisons.

Variation, whatever may be its cause, and however it may be limited, is the essential phenomenon of Evolution. Variation, in fact, is Evolution. The readiest way … of solving the problem of Evolution is to study the facts of Variation.

William Bateson 1894 [1]