Sejtreprodukció

Sejtreprodukció, also known as cell division, is the fundamental process by which a parent cell divides into two or more daughter cells. This process is essential for the growth, repair, and reproduction of all living organisms. In unicellular organisms, cell division is the primary mode of reproduction, enabling populations to expand. In multicellular organisms, it is crucial for development from a single-celled zygote into a complex being, as well as for replacing worn-out or damaged cells throughout life.

There are two main types of cell division: mitosis and meiosis. Mitosis results in two daughter cells that are genetically identical to the parent cell and to each other. This type of division is responsible for somatic cell replication, leading to growth and tissue repair. Before mitosis begins, the cell undergoes DNA replication, ensuring that each daughter cell receives a complete set of chromosomes. The process involves distinct phases: prophase, metaphase, anaphase, and telophase, during which chromosomes are duplicated, aligned, separated, and the cell divides.

Meiosis, on the other hand, is a specialized type of cell division that occurs in germ cells to produce gametes (sperm and egg cells) for sexual reproduction. Meiosis involves two successive divisions, reducing the chromosome number by half. The first meiotic division separates homologous chromosomes, and the second meiotic division separates sister chromatids. This reduction in chromosome number is vital to maintain the correct diploid number of chromosomes when two gametes fuse during fertilization. Meiosis also introduces genetic variation through processes like crossing over.