Biology - Different Stages of Mitosis

[MadmanMurray]

Homework Statement

I'm studying for a biology test at the moment and I'm reading about the M Phase of the cell cycle but I can't really grasp where the boundaries between each phase lies.

I'm reading my notes as well as wikipedia but neither make it clear which stage each process occurs in. For example my notes under the Metaphase heading say "The microtubules have now formed mature spindle fibres that attach to chromosomes via the kinetichore.

Did the spindle fibres occur in the prophase or do they occur in the metaphase. Also what I'm not sure about is whether cytokinesis is part of mitosis or is a separate process. My notes make the distinction between karyokinesis (nuclear division) and cytokinesis (cell division) but they list cytokinesis as one of the stages of mitosis. Wikipedia on the other hand defines cytokinesis as a process that occurs directly after mitosis. Which is it? Is cytokinesis a part of mitosis? If not then would karyokinesis basically encompass all of mitosis?

Homework Equations

The Attempt at a Solution

 

[Ouabache]

Homework Statement

I'm studying for a biology test at the moment and I'm reading about the M Phase of the cell cycle but I can't really grasp where the boundaries between each phase lies.

I'm reading my notes as well as wikipedia but neither make it clear which stage each process occurs in. For example my notes under the Metaphase heading say "The microtubules have now formed mature spindle fibres that attach to chromosomes via the kinetichore.

Try looking at additional references, besides class notes and wiki.
This http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html describes microtubule attachement at the kinetichore, occurs during prometaphase.

Did the spindle fibres occur in the prophase or do they occur in the metaphase.

Spindle fibers form during prophase (see last reference)

Also what I'm not sure about is whether cytokinesis is part of mitosis or is a separate process. My notes make the distinction between karyokinesis (nuclear division) and cytokinesis (cell division) but they list cytokinesis as one of the stages of mitosis. Wikipedia on the other hand defines cytokinesis as a process that occurs directly after mitosis. Which is it?

It sounds like they are playing with semantics. Cytokinesis, does follow mitotic division of the organelles & nucleus. It is where the cell pinches off, making two separate daughter cells. It is often considered part of the mitotic process. (see last reference).

 

[Blueshift5]

The process of mitosis can be divided into four main stages: prophase, metaphase, anaphase, and telophase. Each stage has distinct characteristics and events that occur. The boundaries between each phase can be determined by the specific changes that take place in the cell.

In prophase, the chromatin (loosely packed DNA) condenses into visible chromosomes. The nuclear envelope breaks down and the centrosomes move to opposite poles of the cell, forming the mitotic spindle. This is where the spindle fibers are formed.

In metaphase, the chromosomes line up along the equator of the cell and the spindle fibers attach to the kinetochore of each chromosome. This is the stage where the microtubules have formed mature spindle fibers that attach to the chromosomes, as mentioned in your notes.

In anaphase, the sister chromatids are separated and pulled towards opposite poles of the cell by the spindle fibers.

In telophase, the nuclear envelope reforms around the separated sister chromatids and the cell prepares for cytokinesis, which is the process of cell division.

Cytokinesis can occur either during or after mitosis, depending on the type of cell. In animal cells, cytokinesis occurs after mitosis, while in plant cells it occurs during mitosis. So, your notes and Wikipedia are both correct in their descriptions of cytokinesis. It can be considered a part of mitosis, as it is the final step in the division of the cell, but it is also a separate process.

In summary, the boundaries between each phase of mitosis can be determined by the specific changes that occur in the cell, such as the formation of spindle fibers in metaphase. Cytokinesis can be considered a part of mitosis, but it is also a separate process that occurs after or during mitosis. Karyokinesis encompasses all of mitosis, as it refers to the division of the nucleus, which is the main focus of mitosis.