Does anyone know why my brother's dog would have white flakes(that look like dandruff) running through his black fur?

Probably didn't rinse all of the shampoo out last time, or he has dry skin. Try using fish oil in his food.

Thanks, but what's fish oil?

Are these things actually moving, or do they stay put? If they are moving, I would think of lice. There is also a parasite called Chyletiella (not sure that is spelled right) that causes a condition called "walking dandruff". If they are on the move, its time for a visit to the vet.

They are not moving

If the air is dry, it will cause the skin to be dry and flaky as well. I currently live in an area classified as the edge of the high desert, and am constantly running a humidifier to get the humidity up from around 15% to a much more comfortable 40%. Unfortunately, running central air or heat dries the air out.

Does anyone know why my brother's dog would have white flakes(that look like dandruff) running through his black fur?

A dull coat and dry skin flaking, is also another symptom of worms.

(referring to your other question)

Talk to your brother and your parents, and get the poor dog to your local vet.

I once took my schnauzer to the vet. I had him up on the table and I noticed white flaking. It looked terrible. The Doctor told me that because a dog doesn't sweat sometimes they flake. And they flake a lot more when they are stressed out. Make sure the pup is getting lots of exercise and nothing is stressing him out. But it would seem to be normal.