How can you explain how genetic similarities are due to common ancestry? Where do we get our DNA from?

Actually our genetic code is unrepeatable, the union of the female x chromosomes of our mother and chromosomes and of our father, generate a diploid cell with a UNIQUE cellular genetic code.

What shows our descent from the same ancestor is mitochondrial DNA, this DNA is the same and is repeated throughout the human race.

Explanation:

Mitochondrial DNA is circular and is found in our organelle called mitochondria, responsible for cellular respiration and formation of the energy currency ATP-

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: