1. DNA Replication:
* Before a cell can divide, it must duplicate its entire genome, which includes all its DNA.
* This process, called DNA replication, creates an exact copy of each chromosome.
* The DNA molecule unwinds, and each strand serves as a template for building a new complementary strand.
* Enzymes called DNA polymerases add nucleotides to the new strands, ensuring that the base pairing (A with T, and G with C) is accurate.
* The result is two identical copies of the original DNA molecule.
2. Chromosomes:
* The duplicated DNA is organized into structures called chromosomes.
* Each chromosome consists of two identical copies called sister chromatids, held together at a region called the centromere.
3. Mitosis or Meiosis:
* The cell then enters either mitosis (for growth and repair) or meiosis (for sexual reproduction).
* Mitosis: The duplicated chromosomes are separated and distributed equally to the two daughter cells, ensuring each cell receives a complete set of genes.
* Meiosis: The chromosomes undergo two rounds of division, resulting in four daughter cells, each with half the number of chromosomes as the original cell. This is crucial for the formation of gametes (sperm and egg).
4. Gene Expression:
* Once the cell division is complete, the daughter cells inherit the same genetic information as the parent cell.
* However, gene expression, or the activation of genes, can vary between cells. This allows cells to differentiate and perform specialized functions within the organism.
In summary:
Cell division ensures that each new cell receives a complete copy of the parent cell's genes. This process is vital for the growth, repair, and reproduction of organisms. The genes themselves are not fundamentally altered during division; rather, they are faithfully replicated and distributed to the daughter cells.
