Cell Cycle and Mitosis

Prophase

• Longest phase of Mitosis

• The nuclear envelope (separates the nucleus from the cytoplasm) begins to disappear

• Centrosomes move away from each other

• Chromatin in the nucleus begins to condense and become visible as distinct chromosomes

• The nucleolus disappears

• Centrioles begin moving to opposite ends of the cell

• Fibers extend from the centromeres

• Some of these fibers cross the cell to form the mitotic spindle

Prometaphase

• Nuclear envelope fragments/dissolves

• Proteins attach to the centromeres and form kinetochore

• Microtubules attach to the kinetochores and the chromosomes begin moving

Metaphase

• Centrosomes are now at opposite poles of the cell

• Chromosomes are located at the equator of the cell (metaphase plate)

• Spindle fibers align the chromosomes along the equator

• Microtubule complex is now called the spindle

Anaphase

• Shortest phase of Mitosis

• Sister chromatids are pulled apart to opposite poles as the spindle fibers shorten

• Chromatids are now individual chromosomes/daughter chromosomes

• At the end of anaphase the poles have equivalent amounts and types of chromosomes

Telophase

• The spindle apparatus disassembles and the cell prepares for cytokinesis

• The 2 daughter cell nuclei begin to form around each set of daughter chromosomes

• Nuclear envelopes begin to form from the parent/original fragments

• Chromosomes “become less condense” - uncoil into chromatin

• Mitosis is complete with the completion of the two nuclei regions

Centriole

A cylindrical structure coming in pairs, found inside the centrosome. They are responsible for the organization of microtubules and are essential in cell division through anchoring of spindle fibers. Move to opposite poles of the cell during Prophase. (the pairs duplicate during interphase, specifically the S phase)

**Not found in plant cells

Centrosome

A cellular structure that serves as the main microtubule organizing center of the cell and is crucial for the organization of the spindle fibers during cell division. It consists of a pair of centrioles and densely packed proteins, and is involved in regulating the cell cycle.

Centromere

The region at which the sister chromatids are connected and constricted. When the daughter chromosomes are pulled to each side of the dividing cell, they form a v shape as they are pulled from the kinetochores on the centrosome by the spindle fibers.

Kinetochore

Protein complexes which assemble on the centromere. The spindle fibers latch onto the kinetochores during anaphase, and pull the daughter chromosomes to opposite sides of the cell, forming a v shape.

Chromatid

One of the identical pieces of a chromosome - come in pairs called sister chromatids - two pairs of sister chromatids make up a chromosome, held together by the centromere