What in the human brain do addictive substances like nicotine react with?

Here's one way to follow the scientific method. place the missing steps in the correct position in the process.

You can tell from this karyotype that the individual is female because the karyotype has two chromosomes labeled

Astudent is looking through a microscope at some cells of an onion root tip. many of these cells are undergoing division since the root tip grows quickly and requires more cells. which cell most recently underwent metaphase? w x y z