Ruth Lin, 47985106
FRST302 Assignment 2
Jan 31, 2015

Describe the activities of chromosomes and microtubules in the cell cycle, including all phases of mitosis and meiosis.
Mitosis is a part of the M phase in a cell’s life cycle process whereby cellular division occurs to form two genetically identical daughter cells. The cell cycle consists of the interphase phase and the M phase. The interphase phase represents the period between cells divisions, where the cell grows and develops. The M phase (mitotic phase) represents the period of active cell division, whereby copies of the cell’s chromosomes (sister chromatids) separate, so that a duplicate set of genetic information can be passed down to each of the daughter cells. Mitosis is often …show more content…
Each chromosome is made up of two genetically identical sister chromatids that are joined together by a centromere. Two centrosomes, organelles responsible for microtubule organization, move away from each other in opposite directions, forming the mitotic spindle, a network of microtubules and other machinery that will move chromosomes later on. At the end of prophase, the nucleolus within the nucleus dissolves.

Prometaphase: The nuclear membrane disintegrates. The chromosomes also form kinetochores, protein structures on the chromatids where spindle fibers may attach. Afterwards, microtubules from each of the opposing centrosomes will attempt to attach to the kinetochores corresponding to the sister chromatids on a chromosome. After all the chromosomes have been successfully anchored, the spindle microtubules move against each other, moving the chromosomes toward the center of the cell.

Metaphase: The chromosomes align up at the center together along a single plane termed the metaphase plate. The even alignment is the kinetochores microtubules radiating out from each of the opposing centrosomes counterbalancing each …show more content…
The sister chromatids are able to move towards the spindle poles because of the degeneration of tubulin in the corresponding kinetochore microtubules, causing the spindle fibers to shorten and pull the sister chromatids apart. The separated chromatids are now each considered daughter chromosomes.

Telophase: The daughter chromosomes arrive at the spindle poles of the parent cell. Afterwards, the mitotic spindle dissolves, nuclear membranes are formed around each set of daughter chromosomes, and two separate nuclei are formed within the parent cell. The condensed daughter chromosomes uncoil and lengthen, returning to original chromatin state.

Telophase is followed by cytokinesis, marking the end of the cell cycle whereby cytoplasm is divided to form two daughter cells.

Meiosis is a form of cellular division that involves two fissions of the nucleus to form gametes, or sex cells that have half the number of chromosomes the original parent cell had. Meiosis is the underlying process behind sexual reproduction, whereby the sex cells (egg and sperm) and combines to form new, genetically different offspring. Meiosis is made up of two distinct phases: Meiosis I and meiosis II. Each meiosis stage is made up of 4 stages of their own: Prophase, metaphase, anaphase, and