Genes provide instructions to cells in the body telling them what to do and not do in order to function optimally. Small changes in genes, called mutations, can have major consequences. Similar to a glitch in a computer’s coding, a glitch in gene coding can cause a cell’s system to go haywire. Not all mutations are bad, however. The process of adaptive evolution selects for mutations that promote rapid and unchecked growth, both in yeast populations and in cancer.