The Answer Is 2 Parent Cells
2 examples -
1.) in italy, ( limone ) a unique mutation protects them from developing atherosclerosis,
2.)theres mutation in bacteria too, this mutation allows bacteria to survive in the presence of antibiotic drugs, leading to the evolution of antibiotic-resistant strains of bacteria.
About 10% because I know about 90-95% of DNA is junk DNA(doesnt perform serious function)