Biologists can now control genetic inheritance in mammals with a CRISPR/Cas9-based approach, which allows geneticists to alter parts of the genome by removing, adding or altering sections of the DNA sequence. Scientists have sought a way to make precise changes to the genome of living cells for a long time, and now they actually can. You may ask, what are CRISPR and CAS9? Why are they important? Simply put, “The functions of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and CRISPR-associated (Cas) genes are essential in adaptive immunity in select bacteria and archaea, enabling the organisms to respond to and eliminate invading genetic material.” Thus, this recent discovery has created the groundwork for developing new ways to fight diseases. UC San Diego researchers are responsible for this breakthrough. First, they injected a mouse with an engineered active genetic “CopyCat” DNA element into a Tyroisinase gene. The Tyroisinase gene determines fur color. The CopyCat element “disrupts” both copies of the Tyroisinase gene, causing the mouse to have white fur instead of black. The CopyCat element, however, could not spread through a population by itself, unlike the CRISPR/Cas9 systems, which could. This approach, though, was effective only in female mice, not in male ones, likely because of timing differences in meiosis – “a process that normally pairs chromosomes to shuffle the genome and may assist this engineered copying event.” The findings are nonetheless a success. Scientists are optimistic they will be able to alter multiple genes and traits using the same techniques in the near future. Cooper, one of the researches, summed up their achievement nicely: “We’ve shown that we can convert one genotype from heterozygous to homozygous. Now we want to see if we can efficiently control the inheritance of three genes in an animal. If this can be implemented for multiple genes at once, it could revolutionize mouse genetics,” said Cooper. More importantly, these findings continue to speed up research into diseases like cancer and mental illness.