As if Amazon hadn’t become a big enough part of our lives, the website is now increasingly the place people are going to find if they’re of African heritage or if their children are at risk for certain rare genetic conditions.

DNA-testing companies that offer everything from ancestry information to tests for common inherited diseases are projecting record sales over the holiday season, with Amazon serving as a brand new marketplace for many of them.

Ancestry, 23andMe and dozens of other genetics companies all started selling on Amazon in the “home tests” sub-category in the past year or two, with the bigger players working closely with Amazon to make that happen.

Among the first to initiate sales on the website was Ancestry, which started offering a DNA test for lineage and family connections through the marketplace in 2015. At that time, the company was selling 400 to 500 sets a day, a number that swelled to close to 1,300 a day by late 2016, said Vineet Mehra, Ancestry’s chief marketing officer.

It’s proved to be a larger-than-expected chunk of sales for Ancestry, which directs the bulk of its marketing and advertising to its own site.

Mehra said the Amazon channel has grown from being virtually negligible in 2015 to represent about 5 percent to 10 percent of overall sales. He expects sales via Amazon to jump further in 2017, but he declined to share figures.

The company has sold a total of more than 6 million tests for $79 apiece (recently down from $99).

Amazon featured both Ancestry and chief rival 23andMe on Prime Day, prompting a big spike in sales. They could get another boon in the next week, thanks to Black Friday and Cyber Monday.

23andMe declined to provide a breakdown of its sales on Amazon. Helix, another large genetic-testing company, also declined to share numbers as many of its health tests were only made available on Amazon in the past few days, said CEO Robin Thurston.

For Amazon, these health tests are a growing slice of its burgeoning medical supplies and equipment business.

They’ve also offered a way for the company to roll out health products like cancer risk tests from Color Genomics, that require a doctor’s prescription. Last November, Good Start Genetics was the first to partner with Amazon to sell home tests that tell would-be parents the potential genetic risks facing their kids. CNBC reported this year that Amazon has been mulling a move into the prescription medication business.

Products from Ancestry don’t require a doctor’s note and can be offered to Amazon Prime customers. According to Mehra, it’s also an opportunity to reach an entirely new base of customers, who typically only purchase consumer products on Amazon.

23andMe sees Amazon as an opportunity to learn more about its own customers.

“Amazon provides us with valuable consumer insights, promotional opportunities and best-in-class logistics,” said Jon Ward, 23andMe’s vice president of consumer marketing, in an e-mailed statement to CNBC. “We hope to expand our relationship with Amazon in the coming years.”