The muscle cells had mitochondria with a "paternal" genetic defect.

The muscle cells had mitochondria with a "paternal" genetic defect.
It is our differences, our diversity which makes all of us, of the same species, who we really are as individuals. Humans are more than 99.9% of us identical.

"Truth and morning become light with time." — Ethiopian Proverb
The more sure you are of science or politics the more things change. Just when the facts were about as solid as you thought they could be here comes a different premise.

Scientists in Denmark turned biology on it’s head with what was the accepted wisdom about mitochondria. What you thought you knew about mitochondria was probably wrong if you thought your mitochondria only comes from your mother. It appears there is an exception.

In every cell in your body you have mitochondria, lots of them and the assumption has been you get it from your mother. They are small turbo-charged power generators which appears to be evolved from bacteria (according to a theory by Lynn Margolis a few years ago) which is an organelle which lives outside the nucleus and generates ATP, the fuel necessary for life.

Mitochondria are little energy generators which manufacture the energy we need to live.

These little organelles are as small as bacteria which are one hundred thousand times smaller than your cells. They make ATP which fuels everything in your body. They are so small that you could take a billion of them and easily fit them on a grain of sand.

As often happens with science, theories are constantly being tested and new research improve on those theories. Danish scientists, Marianne Schwartz, a geneticist at Copenhagen University Hospital, et al, have published their research in the New England Journal of Medicine, which document an exception to the assumption that mitochondria is exclusively from mothers. They discovered muscle cells containing paternal mitochondria.

The muscle cells had mitochondria with a "paternal" genetic defect. Other cells; in blood, skin and hair did not have the defect and the genetic pattern indicated they were "maternal" mitochondria.