Mitosis is the form of cell division used by most cells for growth, repair, and replacement. The fundamental requirement of this process is to create new cells that are genetically identical to the original cell. To achieve this, the cell must ensure that the exact number of chromosomes is maintained and accurately passed on to the newly formed cells.
The Purpose of Mitotic Division
Mitosis functions primarily to produce two daughter cells that are genetic duplicates of the parent cell. This process is essential for the growth of a multicellular organism from a single fertilized egg. In an adult, mitosis serves as the means for tissue repair, replacing cells lost due to normal wear and tear.
The division ensures that the entire genetic material is copied and equally divided. Since the resulting cells are identical, mitosis is also the basis for asexual reproduction in many single-celled organisms. The process is controlled to prevent errors that could lead to cells with incorrect chromosome numbers.
Understanding the Chromosome Baseline
A chromosome is a tightly packaged structure made of DNA and associated proteins that contains the organism’s genetic instructions. In humans, non-reproductive cells, known as somatic cells, contain two complete sets of chromosomes, referred to as the diploid state. One set is inherited from each biological parent, resulting in matched pairs.
For a human somatic cell, the total number of chromosomes is 46, consisting of 23 pairs. This 46-chromosome count represents the baseline for the parent cell before division begins. The function of mitosis is to conserve this exact count in the new cells.
The Final Count in Daughter Cells
After a parent cell completes mitosis and the cytoplasm divides, each of the two resulting daughter cells contains the exact same number of chromosomes as the original cell. For example, if a human parent cell begins with 46 chromosomes, each daughter cell will also have 46 chromosomes. This outcome is why mitosis is sometimes called “equational division,” as it maintains the chromosome number.
Before mitosis begins, the cell must duplicate its entire DNA content during interphase. This replication creates two identical copies of each chromosome, which remain joined together as sister chromatids. Although the DNA content temporarily doubles, the chromosome count is considered unchanged because the sister chromatids are still physically connected.
The maintenance of the chromosome number relies on the separation of these sister chromatids during anaphase. During anaphase, the connection holding the sister chromatids together breaks, and they are pulled apart to opposite ends of the cell. Once separated, each chromatid is considered a full chromosome, ensuring a complete set moves to each future daughter cell.
This equal distribution mechanism guarantees that each new cell receives a full, identical set of the original chromosomes. The final count in each daughter cell preserves the diploid state necessary for the organism’s body cells.
Mitosis Compared to Meiosis
The maintenance of the chromosome number in mitosis contrasts sharply with the outcome of meiosis, the other primary form of cell division. Mitosis occurs in somatic cells, while meiosis is specialized for producing reproductive cells, known as gametes (sperm and egg cells).
Meiosis is a reduction division that halves the chromosome number of the parent cell. If a human parent cell starts with 46 chromosomes (diploid), the cells produced by meiosis will contain only 23 chromosomes (haploid). This reduction is necessary so that when two gametes fuse during fertilization, the species-specific chromosome number is restored in the offspring.
The fundamental difference lies in their purpose. Mitosis creates genetically identical cells to replace and grow tissue, while meiosis creates genetically unique cells with half the chromosome count for sexual reproduction.