Cell Division (Reproduction )

Lab -3-
Cell Division (Reproduction ).

The first stage of growth in a living organism is the formation of new cells by a process know an cell division, which occurs most commonly in the meristematic or growth tissues of plants. Cell division involves two phases:-
1- The division of the nucleus into nuclei in process known as Mitosis.
2- The division of the cytoplasm as a result of the formation of a new cell wall, separating and dividing the original cell into new cells in process known as Cytokinesis.

1- Mitosis is a process of nuclear division in which chromosomes divide lengthwise, separate, and form 2 identical nuclei. Mitosis is usually accompanied by cell division, which involves the formation of a new cell wall between the 2 identical nuclei. In plants, good sites to observe mitosis are in root tips, shoot apices, and newly developing leaves. This is done by making thin sections of the tissues, mounting them on slides, staining them with acetocarmine or Feulgen stains, then observing the sections with the high power or oil immersion lens of an optical (light) microscope.

The Cell Cycle
The period when the nucleus is between divisions is called interphase. During interphase is a period of replication of cytoplasmic organelles, followed by a period when chromosomes are duplicated, then a period when spindle fibers (bundles of microtubules) are made. Phases of mitosis are prophase, metaphase, anaphase, and telophase. Interphase and the 4 phases of mitosis constitute the cell cycle.

Phases of Mitosis