 |
Introduction |
| |
One of the main ideas in the modified cell principle is that new cells arise from pre-existing cells (Omnis cellula e cellula). Every new cell formed must inherit not only the nucleus which contains the genetic information, but also should inherit the cell organelles that are required to express this genetic information. This process occurs by division of the pre-existing cell and is called cell reproduction or cell division. In spite of the enormous diversity in organisms, the mode of cell division is essentially similar indicating the Unity of Life. |
|
Cell Division |
| |
Cell division forms a mode of reproduction in unicellular organisms. In multicellular organisms it is responsible for embryonic development and growth of the adult organism. It is also involved in repair and regeneration. Both asexual and sexual reproduction requires cell division. |
|
Cell Cycle |
| |
Every cell that is capable of undergoing division passes through a cyclic sequence of events involving growth and division. It is called Cell Cycle. It encompasses the entire sequence of events that occur in a cell from the time it is formed from its parent cell till the time of its own division into daughter cells. |
|
Mitosis |
| |
It is a common type of cell division that occurs in all the cells of an organism. Hence, it is commonly called as somatic cell division. In mitosis, the resulting daughter cells will have the same number of chromosomes and contain the same amount of DNA, as that of the parent cell. Hence, mitosis is commonly described as equational division. |
|
Meiosis |
| |
It is a type of cell division that occurs only in the reproductive cells and hence it is known as germ cell division. The daughter cells resulting from meiosis will carry half the number of chromosomes and half the amount of genetic material compared to the parent cell. Hence, meiosis is also known as reductional division. |
|
Differences between Mitosis and Meiosis |
| |
Results in the formation of two daughter nuclei having the same no. of chromosomes as that of parent cell. |
|
Karyotype |
| |
Chromosome number is a species-specific character. The complete set of chromosomes in the body cell of a species is known as karyotype. For example, the 23 pairs of chromosomes found in the somatic cells represent the human karyotype. |
|
Summary |
| |
According to the modified cell principle, new cells arise only from pre-existing cells. Cells transfer their genetic information only by way of cell division. |
