A nucleus consists of a nuclear membrane that surrounds it, within the membrane there is a nucleolus which can be compared metaphorically to the yolk of an egg in appearance. The nucleolus is surrounded by nucleoplasm which is quite like the cytoplasm.
The phase during which sister chromatids aggregate along the equator of the cell is called the metaphase.
The image shows the process of cell division through mitosis. The mother cell divides into two genetically identical daughter cells in mitosis. There are four main phases in the mitosis process. They are: prophase, metaphase, anaphase and telophase. In the metaphase, the highly condensed sister chromatids line up along the equator of the cell by binding to the microtubles that form the skeleton of the cell. These kinetochores line up the chromatids at the equator to initiate their separation.
They are formed primarily on the cell's Ribosomes.
Semipermeable means the cell membrane can pick and choose what goes out of it and into it. At least, that's what I believe it is.