It might be dumbing-this-down-for-ponies. Ponies generally accept 'it happened because magic' as a be-all end-all answer.
"...Good choice," says Handy after a moment or two of abashed, silent mouth-flapping. Giving an almighty sniff, he reviews his case and tries to decide where to start. "Time Lords have triple helix DNA," he begins. "The third strand governs a series of self-replicating biogenic particles, and when those get triggered, he'll undergo what's called regeneration -- everything gets repaired and reorganized down to the cellular level -- to a lesser extent in the brain, though -- and when he comes out of it, he's a whole new him. New face, new body, new personality to an extent even though the memories stay. Are you following?"
He knows she has to have been telling the truth about her course of study, but if she's going to ask for the scientific version, well, this is a bit of a test for her.
no subject
"...Good choice," says Handy after a moment or two of abashed, silent mouth-flapping. Giving an almighty sniff, he reviews his case and tries to decide where to start. "Time Lords have triple helix DNA," he begins. "The third strand governs a series of self-replicating biogenic particles, and when those get triggered, he'll undergo what's called regeneration -- everything gets repaired and reorganized down to the cellular level -- to a lesser extent in the brain, though -- and when he comes out of it, he's a whole new him. New face, new body, new personality to an extent even though the memories stay. Are you following?"
He knows she has to have been telling the truth about her course of study, but if she's going to ask for the scientific version, well, this is a bit of a test for her.