The continuity of life is based upon cell
How many cells do you have?
The average eukaryotic cell is about 100 Ám (100 x 10^-6 m. = 10^-4
You have 200 trillion (2 x 10^14) somatic cells (p. 230).
Total length of your cells lined up end-to-end: (2 x 10^14) x (10^-4
m.) = 2 x 10^10 m. = 2 x 10^7 km.
The earth's circumference is 40 million m. (40 x 10^6 m. = 4 x 10^7 m.
= 4 x 10^4 km.
2 x 10^7 km. / 4 x 10^4 km. = 500: your cells can wrap around the
earth 500 times.
Updated Apr 01, 2011 by Peter Chen
Functions of Cell Division.
Reproduction. An amoeba, a single-celled eukaryote, is dividing into
two cells. Each new cell will be an individual organism. Growth and
development. A sand dollar fertilized egg divides into two cells.
Further division and development yield a multicellular organism.
Tissue renewal. These dividing bone marrow cells will give rise to new
The mitotic phase consists of mitosis,
the division of the
the division of the
Stages of mitosis.
G subphase of Interphase prophase prometaphase metaphase anaphase
telophase and cytokinesis
G2 of Interphase.
A nuclear envelope bounds the nucleus.
The nucleus contains one or more nucleoli, where ribosomes are
Chromosomes have been duplicated, but are not yet visible under the
In animal cells, centrosomes are also replicated.
The chromatin condense into discrete chromosomes observable with a
The nucleoli disappear.
The replicated centrosomes move apart, toward opposite "poles" of the
The mitotic spindle begins to be formed from microtubules, which
radiate from the centrosomes and appear as star-like asters.
The nuclear envelope fragments.
The spindles continue radiating from centrosomes, which are at
opposite "poles" of the cell.
Each of the 2 chromatids of a chromosomes has a kinetochore, which
attach the chromatid to the spindle microtubules at the centromere.
The chromosomes convene on the metaphase (equatorial) plate.
For each chromosome, the kinetochores of the sister chromatids are
attached to spindle microtubules coming from opposite poles.
The 2 sister chromatids are transported by spindle microtubules toward
opposite ends of the cell,
The non-kinetochore microtubules lengthen.
Each chromatid is now a full-fledged chromosome.
Two daughter nuclei begin to form.
Nuclear envelopes and nucleoli reform.
The chromosomes become less condensed.
Mitosis, the division of one nucleus into two genetically identical
nuclei, is now complete.
Animal cells Plant cells
Cytokinesis in animal cells.
In animal cells, a cleavage furrow forms, pinching the plasma
Then a contractile ring of microfilaments splits the cell.
Animal mitosis movie:
Cytokinesis in plant cells.
In plant cells, a cell plate grows between the "daughter" cells,
making a new plasma membrane.
Then new cell walls made of cellulose are formed along the new
Review: Mitosis and Cytokinesis
Mitosis and Cytokinesis Video (Newt cell)