Genetic Terms

Onion Root Tips

 Growth in an organism is carefully controlled by regulating the cell cycle. In plants, the roots continue to grow as they search for water and nutrients. These regions of growth are good for studying the cell cycle because at any given time, you can find cells that are undergoing mitosis. 

Onion root tips are extremely popular for viewing the different phases of mitosis because the chromosomes are large and and very dark when stained.

1)    Interphase-is considered the first and last stage of plant cell division. It is the stage in which the cell is growing in size and replicating its DNA in preparation for division. The nucleus is apparent.
2)    Prophase-During Prophase the nuclear envelope starts to break down and all the chromosomes start to coil up in the center of the cell.
3)    Metaphase-is the middle stage at which point all the chromosome pairs line up in the center of the cell along spindle fibers that pull to either side of the cell.
4)    Anaphase-The spindle fibers become shorter and pull each chromosome pair apart to the opposite ends of the cell.
5)    Telophase-The final stage of cell replication.The nuclear envelope is reformed. Cytokinesis takes place. A new cell wall is created down the center and two daughter cells are formed.