Xinjiang province is the site of intense surveillance and oppression, even by Chinese standards; it's home to the largely Muslim Uyghur minority, and a combination of racism and Islamaphobia drive a uniquely intrusive grade of policing and surveillance.
The Chinese government is undertaking a "Population Registration Program" that involves gathering "DNA samples, fingerprints, iris scans, and blood types of all residents in the region between the age of 12 and 65." Nominally, it's part of a fitness program to screen for diseases, target health care, and create electronic health records.
Human Rights Watch points out that as laudable as these goals are, they take on a different complexion when they're used as a program that exclusively targets people in a region known for ethnic-based oppression.
As well as concerns about the human rights of Uyghurs being harmed, another issue is that Xinjiang's Population Registration Program may be used as a trial before rolling out DNA collection to the entire Chinese adult population, just as is happening with a national facial recognition database. Although such a large-scale genetic database would have been infeasible a few years ago, advances in sequencing and dramatic falls in data storage and processing costs mean that it could probably be built now. And if China goes down this route, the fear has to be other countries will follow, just as they are doing in the realm of online surveillance.