He noticed that some of the progeny possessed characters which were not to be found in either of the parental types. He further observed these changed types bred true.
He therefore described these sudden changes as mutations and ascribed them to some changes occurring in the germ plasma of parents.
Even Charles Darwin was aware of mutations, even though he did not use the term (mutations). He was aware of sudden changes occurring in organisms both plants and animals and had used the term sports, to describe them.
The first recorded instance of mutation dates back to 1791, to the pen of Seth Wright, a New England farmer, where appeared a male lamb with short bowed legs. Wright reared this lamb and it bred true.
A lamb with short legs was of great advantage as it could not jump even a low level fence. This short legged breed was called Ancon breed. This breed however became extinct after about eight years.
But the same Ancon sheep appeared some fifty years later in the flock of a Norwegian farmer, representing probably the repetition of the same mutation. Since then a number of mutant types have been discovered.
Hornless individuals in cattle, double toed cats, albino rats, mule footed swine, dwarf cupid sweet pea, double flowered, white flowered varieties of many plants are all mutants. The scientific study of mutations began with the work of Morgan on Drosophila in 1910.
He observed that among a population of red eyed flies, some individuals with white eye appeared and they were predominant among the male individuals.
He further found out that the white eyed gene is recessive to red eye and located on the X chromosome.
Since the male individuals possessed only one X chromosome and the females had two X chromosomes, the recessive character appeared more frequently among males than among females.
After the original discovery of the white eyed mutant in Drosophila by Morgan and his co-workers, a detailed analysis of millions of these fruit flies for over 1-7 years was carried out by different geneticists and nearly 500 gene mutations have been discovered.
Simultaneously other organisms like maize, rodents, pea, snap dragons, poultry, man etc. also have been investigated and scores of mutations have been discovered. Even in microorganisms also mutations have been detected.