Friday, 19 February 2016

MITOSIS: Multiplication by Division

Our body contains trillions of cells (thousands of millions) but everything started from a single cell. This unit cell has the amazing ability of dividing into two, and then four, and then eight and so on, in time becoming a complete organism. The process through which cells divide and divide as to multiply in number and become a complete organism, is known as Mitosis.

During Mitosis, the parent cell divides to form two genetically identical daughter cells. In order to assure a perfect copy of the genetic material in the daughter cells, the parent cell has to duplicate the chromosomes first; this step is called the
Interphase (chromosomes duplicate, and the copies remain attached to each other.) and it is the first phase on the cell cycle process.

After Interphase, Mitosis (the actual cell division process) takes place through 6 subsequent steps: 

Prophase: In the nucleus, chromosomes condense and become visible. In the cytoplasm, the spindle forms.

Prometaphase: The nuclear membrane breaks apart, and the spindle starts to interact with the chromosomes.

Metaphase: The copied chromosomes align in the middle of the spindle.

Anaphase: Chromosomes separate into two genetically identical groups and move to opposite ends of the spindle.

Telophase: Nuclear membranes form around each of the two sets of chromosomes, the chromosomes begin to spread out, and the spindle begins to break down.

Cytokinesis: The cell splits into two daughter cells, each with the same number of chromosomes as the parent.

Some of these steps are easily visible under the microscope. A classic experiment to observe the different phases of mitosis includes the observation of apical meristems of garlic roots (where the growth is greatest and therefore the number of duplicating cells is relatively high).

The garlic root tips are removed and placed in a warm acidic solution (to separate the tissues into small fragments). Further, the sample is washed and stained with 0.1% toluidine blue, a dye for microscopy that has a strong affinity for chromosomes.

On the images below, we can see treated garlic root tips where cells going into different Mitosis phases can be easily identified.

No comments:

Post a Comment