For example, the Beltsville team recently identified an association between DNA markers on chromosome 6 and the amount of protein in milk. Many of these milk proteins are called caseins. But the casein genes are located close to the chromosome's bottom, and we're seeing our effect at a different location on the chromosome much further up. This suggests that there are several different genes that affect important traits like protein content. Eventually, information gleaned from this genetic riddle may offer a way for breeders to select animals whose milk contains even more protein.
Casein proteins are especially important for cheesemaking.
But some caseins are better suited than others to this. With the right genetic tools, Ashwell ventures, there may come a day when cows are bred for milk that contains specific proportions of these cheese-friendly proteins. By marking off chromosome regions, scientists can begin creating a genetic roadmap that can be used to put desirable traits into cows. By Jan Suszkiw, Agricultural Research Service Information Staff.