The condensation of chromatin happens during prophase, resulting in rod-shaped chromosomes that are visible via microscopy. This happens after the replication of genetic material during interphase. The chromosomes are already condensed by metaphase and anaphase.

Metaphase is the stage of mitosis in which sister chromatids line up at the metaphase plate and mitotic spindles interact with the kinetochores of the chromatids. The metaphase plate is the area where sister chromatids line up. This line is imaginary, but is equidistant from both cell poles. The contractile ring will begin forming at a similar location, but the chromosomes lining up at the metaphase plate and the formation of the contractile ring are events in mitosis that are temporally separate, and thus, never actually interact. 

During interphase, the parent cell grows, synthesizes proteins, and replicates its genetic material following the semiconservative model of DNA synthesis. By the end of interphase, the parent cell is nearly double it’s original size, including more cytoplasm, proteins, and organelles, and has a duplicated genome. At the end of mitosis, the parent cell begins the process of cytokinesis, in which a contractile ring of myosin and actin forms in the middle of the cell, pinching off the parent cell into two daughter cells. The resulting two daughter cells are roughly the same size and are genetically identical to each other.

In higher eukaryotic (animal) cells, the nuclear membrane breaks down during prometaphase and two nuclear membranes reform around the segregated genetic material during telophase. This process has been observed under electron and fluorescence microscopy. In lower eukaryotes, such as yeast, the nuclear membrane is maintained, with mitotic spindles either penetrating it or forming within it.

Centrosomes are organelles composed of two centrioles and function as microtubule organizing centers. Centrosomes are duplicated during S phase of interphase, and migrate to opposite poles of the dividing cell to form the mitotic spindle apparatuses. The mitotic spindles originate at the centrosomes, where microtubule regulation occurs.

During prophase of mitosis, microtubules attach to the centromere region of the chromosome. Remember that the centromere is the region that connects the two sister chromatids that compose the chromosome. Specifically, the specialized region of the centromere that the microtubules attach to is called the kinetochore. The centrioles are the structures that make up the centrosomes, which are the microtubule organizing centers from which microtubules originate.

A cell that has completed mitotic anaphase contains separated sister chromatids. A cell at the start of prophase still has chromosomes with attached sister chromatids. This means that a cell in anaphase with eight distinct chromosomes must have had four chromosomes with unseparated chromatids at the beginning of prophase. Once cytokinesis is complete, the resulting cells with each have four chromosomes.

The sister chromatids separate from each other during mitotic anaphase. The daughter cells each receive the same amount of chromatids as the original cell had chromosomes. If sixteen distinct chromosomes exist at metaphase, then sixteen chromatids will go to each of the daughter cells. Recall that during mitosis, a diploid parent cell gives rise to two diploid daughter cells.

Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.

Chromatin serves as a scaffold for DNA and helps regulate gene activity. Chromatin can be condensed, as euchromatin, or loosely packed, as heterochromatin. The compactness of chromatin determines its level of activity. When it is loosely packed, it can be acted upon by DNA replication and/or transcription enzymes, and those genes may be expressed. Centromeres hold sister chromatids together.