Test results reveal what makes a twin white or black

Shirley Wales has non-identical twins, but her son Leo has black skin and her daughter Hope, has white skin.

In order to discover how this genetic phenomenon occurred, Shirley took a DNA test to find out more about her own genetic profile.

She was adopted when she was four years old, and her birth mother is Afro-Caribbean and her British birth father was white. Her DNA tests revealed that, genetically, she was exactly 50% African and 50% European.

Find out more about Shirley's story in Twincredibles, which will be broadcast on Monday 10 October at 21:00 BST on BBC Two, as part of the Mixed Race Season.

READ MORE: What makes a twin white or black?