3B Scientific Cell Division I Chart, Mitosis - Manual (Page 2)

English
Mitosis
At the end of this description you will find illustrations of the 9 phases included. You can use these to
make photocopies for your lessons. By colouring, labelling and correctly arranging the individual phases
your students can easily review and memorize what they have learned.
Free colour illustrations of the individual stages are also available on the Internet at
http://www.3bscientific.com
1. Interphase, Stage of the G
1
Phase
Inside the cell the nucleus with the nucleolus (1) and its nuclear membrane (2) can be seen. The nucleus
also contains the not yet helical DNA (3) with the genetic information.
The cell itself receives its stability and shape from very fine tubes, the so-called microtubules (4) extending
through the cytoplasm. The microtubules control, among other things, the cell movements and the intra-
cellular transport processes.
In the cytoplasm, the endoplasmic reticulum (5) can be seen. This is an intertwined tube system mainly in
charge of the innercellular transport of water and ions. The membrane of the endoplasmic reticulum has
ribosomes attached to it, whose function is the production of proteins.
The Golgi complex (or apparatus) (6) can also be referred to as ”cell gland”. It is made up of stacks of
layered hollow sacs (Golgi cisternae), which swell up to vesicles and ”pinch off” (Golgi vesicles) (7). The
Golgi complex receives membrane components and enzymes from the endoplasmic reticulum and its
main function is to collect and distribute secretions and produce lysosomes (digestion vesicles) (8).
The main job of the lysosomes is breaking down cell components. This can occur either from within the
cell towards the outside (= exocytosis) or within the cell (= intracellular digestion). The organelles in charge
of producing energy for the cell are the mitochondria (9).
The job of the centrioles (10) is to build up the cleavage spindle. They are hollow cylinders made up of
longitudinally arranged tubes (microtubules).
Mitosis
English
Mitosis, also referred to as indirect nuclear division or equational division, is the most widespread type of
cell reproduction. In this process, one cell (mother or parent cell) is divided into two daughter cells with
identical DNA (=genes containing hereditary information) and the same number of chromosomes. Mitosis
is vital for the growth and preservation of all living organisms.
The human organism is made up of approx. 10 15 to 10 16 cells. In fast-growing tissues (e.g. intestinal
epithelium) cells are divided by mitosis approx. every 12-35 hours, in slower-growing tissues (e.g. ten-
dons) only approx. every 3-6 months.
In the cycle of a cell, a basic distinction is made between the interphase, referring to the period be-
tween two cell divisions, and the phase of actual division, called mitosis.
A further phase not forming part of this cycle is referred to as the G 0 phase. This is a phase of cell growth
or differentiation without preparations for a division. In this phase the cell can irreversibly lose its power
of division (e.g. muscle cells), or, after a G
0
phase of variable length, it can re-enter the cell cycle which
then begins with the G
1
phase.
The interphase comprises 3 stages:
➢
G
1
phase (presynthesis) In this phase the cell begins to prepare for the forthcoming mitosis. The
growth of all parts of the cell is activated and the centrioles are duplicated. In fast growing cells the
duration of this phase is approximately 3 hours.
➢ S phase (synthesis)
In this phase the amount of DNA is doubled by replication as a further preparation for the forth-
coming cell division. In fast growing cells the duration of this phase is approximately 8 hours.
➢ G
2
phase (postsynthesis)
At this stage the last preparations for entering into mitosis are made. The chromosomes are con-
densed and the DNA is ”proofread”. At the end of this phase, cells in human/animal tissue cut off
the cell contacts with neighbouring cells, round off and frequently increase their volume through the
intake of fluid. In fast-growing cells the duration of this phase is approx. 4 hours.
The mitotic cycle comprises the following phases:
➢
Prophase
➢ Early prometaphase
➢ Later prometaphase
➢ Metaphase
➢ Early anaphase
➢ Later anaphase
➢ Telophase
➢ Cytokinesis
Duration of all phases in fast-growing cells: approx. 1 hour
The 3B Scientific ® model series on Mitosis (product no. R01) and the wall chart on mitosis (V2049M,
V2049U) show a typical mammal cell at an enlargement of approximately 10,000 times. In the lower
third of the models/illustrations the cell organelles are shown as if opened up.
The 3B Scientific ® model series on mitosis is supplied in a storage system, which is equipped with a
hanging device. The model series can thus be simply hung on a wall in order to save space. The models
also have magnets at the rear so that they can be arranged on magnetic boards in the classroom for tea-
ching purposes.
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