Scientists in California have used CRISPR, a gene editing tool, to engineer the genome of a bull calf. The idea is this: the region on the Y chromosome that initiates male development (the sex determining region, SRY) is actually not that large. So the scientists just transferred it onto another chromosome. Offspring that inherit this altered chromosome should have a male phenotype regardless of whether they also have a Y chromosome. So instead of 50% males, this calf is expected to have 75% phenotypically male offspring. (It is just 75% as the offspring is not guaranteed to inherit the altered gene from the father, they could instead also inherit the unaltered copy from the mother). Why would you want to have 75% male instead of 50%? The simple answer is: they yield more meat.