You could inherit the DNA from any of the carriers who were alive at that time not just King Tut. The reason King Tut is highlighted is that most of the mummies from the Egyptian royal families got destroyed over the years due to looting of their graves, so their DNA isn't available to test. The gene in question are located on the Y-chromosome, so the other males in the royal family shared it too.
This is analogous to the testing on the male descendants of Sally Hemmings. The hype was that it proved that Thomas Jefferson fathered children with Sally Hemmings. All that was proved was that any one of several male relatives of Thomas Jefferson could also have fathered those children.
LISTER: What about the photograph?
He pulls it out and examines it again.
LISTER: I'm not the groom. (pointing to another figure in the picture) He is the groom!
CAT: Hey -- she's not as stupid as we thought!
LISTER: Why do women always leave me for total smegheads? Why do they dump me for men who wear turtleneck sweaters and smoke a pipe? I mean, natural yoghurt eaters! Reliable, sensible, dependable, and lots of other words that end in "-ible." He's obsessed with house-prices, and spends half his life in antique fairs looking for bargains and drinking wine. It's never beer, is it, it's always wine! "What do you want on your cornflakes, darling?" "Oh, I'll have some wine, please!" Smeg!
He leans against a wall, bitter and angry. CAT taps him on one shoulder.
CAT: You can tell all that, just from a photograph?
“The gene in question are located on the Y-chromosome, so the other males in the royal family shared it too.”
How SEXIST!
:-)