It's the go-to Christmas present for the person who already has everything. A gift that promises to tell you who you really are and how you're connected to the world.

In this new series for BBC Radio 4, The Gift, journalist and broadcaster Jenny Kleeman meets the men and women whose lives changed forever after they opened a box that contained a DNA test. Exposing scandals, upending identities, solving mysteries and delivering life-changing news - Jenny investigates what happens when genealogy, technology and identity collide.

Millions of people have spat into a tube and sent a vial of DNA to a company like Ancestry and 23andMe. Even if you haven't taken a test, it's likely a fairly close relative has, leaving an equally close version of your genetic code uploaded online, waiting to be discovered. Without us realising, an enormous global DNA database has been created, and shocking secrets once assumed forever hidden are being forced into the light.

Over six episodes, Jenny meets people whose lives have been transformed by at-home DNA tests. Stories told across the series include:

• The man in his eighties whose birthday present DNA test helped expose a shocking scandal at the heart of Harley Street

• The son whose quest to learn more about his late father solves a mystery that has baffled police for over four decades

• The family that learns their youngest son is no biological relation to his father, and turn detective to find the couple who had IVF at the same time as them

• What happens when white supremacists discover they aren’t as white as they thought?

• The woman whose Christmas gift from her sister led her to get a double mastectomy. Plus – how much can life change when you discover you’re living with the Alzheimer’s gene?

Jenny Kleeman says: "We’re now so casual about testing our DNA, and I’ve become fascinated by the unintended consequences of unlocking the secrets contained in our genes. I began to collect extraordinary human stories of secrets, scandals, life-changing health news and even crimes that have been revealed through at-home DNA testing. So many people have now taken a test that almost anyone can be found. What happens when the DNA databases reach a critical mass? And how much do our genes really make us who we are?"

The Gift begins on Monday 11 September at 11am with episodes broadcast on BBC Radio 4 weekly. Episodes will be available to listen back on BBC Sounds.