Mitosis is the process of cell division, which occurs in four stages:
- prophase
chromosomes condense and become visible, appearing as double strands. Each strand is called a chromatid. The nuclear membrane also breaks down.
- metaphase
Spindle fibers form and attach to the chromosomes.
Chromosomes align along the center of the cell.
(Because metaphase chromosomes are highly condensed, scientists
use these chromosomes for gene mapping and identifying
chromosomal aberrations.)
- anaphase
The paired chromatids are pulled to the opposite ends of the cell.
- telophase
The chromatids finish separating and become chromosomes, which once
again lengthen and become diffuse. A new nuclear membrane forms around
each set of chromosomes, and the cell divides in two by cytokinesis,
producing two daughter cells. Each daughter cell has a complete set of paired chromosomes, and is therefore diploid.
Note: Compare with meiosis, the production of gametes, in which there are two cell divisions. Each sperm or egg cell produced contains a complete set of unpaired chromosomes, and is therefore haploid.
References:
National Human Genome Research Institute (NHGRI)
Glossary of Genetic Terms.
and
Lackie, J.M. and Dow, J.A.T., eds. 1999. Dictionary of Cell Biology. 3rd ed. London: Academic Press.
|
