Gradual definitely tending variation, such as may be observed in a group of organisms in the fossils of successive geological levels.
As now employed (first by de Vries), a sudden variation (the offspring differing from its parents in some well-marked character or characters) as distinguished from a gradual variations in which the new characters become fully developed only in the course of many generations. The occurrence of mutations, and the hereditary transmission, under some conditions, of the characters so appearing, are well-established facts; whether the process has played an important part in the evolution of the existing species and other groups of organisms is a disputed question.
The result of the above process; a suddenly produced variation.
The balance of evidence both from the cell-free system and from the study of mutation, suggests that this does not occur at random, and that triplets coding the same amino acid may well be rather similar. Francis Crick
The unique nature about the influenza virus is its great potential for changes, for mutation. Margaret Chan
Although I insist that God has always had the power to intervene directly in nature to create new forms, I am willing to be per-suaded that He chose not to do so and instead employed secondary natural causes like random mutation and natural selection. Phillip E. Johnson
A comparison between the triplets tentatively deduced by these methods with the changes in amino acid sequence produced by mutation shows a fair measure of agreement. Francis Crick
Attempts have been made from a study of the changes produced by mutation to obtain the relative order of the bases within various triplets, but my own view is that these are premature until there is more extensive and more reliable data on the composition of the triplets. Francis Crick