More than one scientific study links early-onset Alzheimer's disease to the mutations of three genes. Once the genes were identified in the first study, why were additional studies conducted? Each gene requires its own separate study. Replication of data is needed to make a valid scientific conclusion. It is unethical to make a conclusion after one study. The results of the first study were most likely flawed.

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.