Robert Heinlein wrote a book, I think it was Time Enough for Love which story included a database where anyone who had four grandparents who lived to X years old could register. Anyone in the database who mated with someone else in the database got a financial incentive. The more children, the more money. That's selective breeding, in this instance for longevity.
Splicing shark DNA onto a human so a country can win swimming events in the Olympics would be genetically modifying.