Mitosis: Cell Division and Reproduction
Mitosis is a process in which a cell divides into two identical daughter cells. It is a vital process in organisms that need to reproduce. This is why it's important to understand how it happens, and how it can help you understand why your body grows and develops in the way that it does.
Interphase: Preparation for Division
During the first stage of mitosis, called interphase (G1 and G2), the cell prepares for division by copying genetic material into two identical copies. This involves a series of steps that include energy replenishment, synthesis of proteins required for chromosome manipulation, and dismantling of the cytoskeleton.
S Phase: DNA Duplication
In the S phase of mitosis, DNA is duplicated into two identical sister chromatids, and centrosomes that give rise to the spindle are replicated as well. In this phase, the cell also performs a check to ensure that each of its chromosomes has correctly attached itself to its own microtubules from both its poles. If a chromosome isn't properly attached, it won't move on to anaphase until the problem is fixed.
Prophase: Chromosome Condensation
Next, chromatin fibers that make up the DNA become coiled and condense into chromosomes during prophase. These chromosomes are made up of two chromatids that are connected at the centromere, or "centre." Early prophase begins by forming the spindle apparatus with its specialized network of microtubules called spindle fibers. These fibers begin extending from opposite ends of the cell and extend all the way to the center, or "cell equator," where they attach to the kinetochores that form on each chromatid during cell division.
Metaphase: Chromosome Alignment
The chromosomes then begin to align at the metaphase plate, which is a symmetrical plate that is lined up across the equatorial plane of the cell. They are held in place by polar fibers that produce equal forces. Once the chromosomes are in position at the metaphase plate, they begin moving toward the center of the cell by using the spindle fibers. Each chromosome has two kinetochores that attach themselves to the microtubules on opposite spindle poles. These kinetochores help in directing the chromosomes to the centromeres on their sister chromatids.
Anaphase: Chromosome Separation
As the chromosomes approach the center of the cell, their chromatin fibers start to become shorter and more twisted. This is a sign that the chromosomes are ready for their final step in division, anaphase. Anaphase occurs when the chromosomes' chromatin fibers are shorter and more twisted, and the centromeres on each chromosome are farther from the center than during prophase. The chromosomes then begin to separate.
Daughter Cells: Identical but Diploid
The daughter cells are identical to the parent cell in every way except for their chromosomes. In addition, they have half the total number of chromosomes, making them diploid. This is a good thing because it allows the cells to reproduce more rapidly and efficiently. This makes it easier for your body to grow new cells and to repair damaged ones.
