Mendel made his discoveries using garden peas. A new generation of biologists made some breakthroughs experimenting with tiny fruit flies. They found that they could change the hereditary information in fruit flies by the use of things like drugs, heat, and x rays. A change in the hereditary information is called a mutation. Most of the time a mutation is bad for the organism.
Genuine monsters can happen.
Very occasionally, however, it can result in an improvement. A fruit fly with more resistance to pesticides, for instance. Or one that can produce more offspring, or fly faster, or get along on less food. After a great many clever experiments with fruit flies biologists were even able to draw maps or fruit genes. But this only whetted the appetite of the scientists.