SINGAPORE — In an era of business buzzwords like “unicorn” and “fintech,” a commercial model built on spitting into a tube might not seem the most propitious idea. But Asia’s nascent DNA testing sector is likely to expand as related technology becomes more affordable and as scientific research advances. Behind the trend is the region’s growing affluence. As tens of millions of people move from the countryside to cities across Asia, so-called “lifestyle” conditions such as diabetes and heart disease become more commonplace as people eat more processed food and replace physically-taxing employment such as farming with sedentary office work. Peering into a person’s DNA can yield insights about susceptibility to particular health conditions or diseases — and a growing consumer awareness of such advances is driving much of the DNA sector’s Asian growth, note companies involved in testing.