STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
OBSERVATIONS REGARDING THE MITOTIC
DIVISION STUDY IN NORMAL AND POLUTED
CONDITIONS FOR THE Betula pendula
Marian CĂRĂBAŞ
Universitatea de Vest “Vasile Goldiş” Arad, Romania
Abstract
By studying germinating Betula pendula seeds untreated with
colchichin, a normal mitosis was observed, but on the other hand at the
colchichin treated seeds a number of anomalies were observed.
Keywords : mitotic division, Betula pendula
INTRODUCTION
During its lifetime, an organism goes trough different steps however
these steps can not take place without cell reproduction. Cell reproduction
can not take place, except after a short training in witch all the cellular
components double.
The succession of all cellular phenomenons that take place at the
birth of a cell and until it divides into 2 daughter cells bear the name of
cellular cycle. The cellular cycle has 2 important independent steps: the
inner phase and the cell division.
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
Fig. 1 Cell Cycle Plan
The length of the cellular cycle is specific to each type of cell (even
to the cells from the same tissue, depending on the position) but also for
each type of specie. Ex: for Allium cepa 12 hours, Zea mays 15 hours,
Pisum sativum 12 hours. For the most part of the eukaryotes, in normal
conditions of feeding and temperature, a mitotic cycle is completed in 24
hours, from which 1-2 represent the mitosis, and the rest, the interphase. In
certain laboratory conditions, some of the animals pass through the mitotic
cycle in 10 hours and the bacteria in 20 minutes.
The interphase is the replication stage of the cellular cycle and it
lasts approximately 90% of the time, and the cellular division is the
distributive stage and in lasts approximately 10% of the time.
The interphase (Intrekinesio) represents the metabolic stage of the
cellular cycle due to some synthesis of plastically substances, energetic and
catalithyc, which have as purpose doubling the quantity of genetic
information and amplifying the number of cellular organoides constitute
from the spare of the cells, without it, the division can` t take place.
The interphase is caught between the intervals of time that separates two
successive divisions of the cell. In 1958 A. Howard and R. Pelo, described
that during the interphase which they considered to be the preparatory stage
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of the cellular cycle, 3 periods: G1-presynthetic, G2- synthetic, G3- post
synthetic.
G1 period – presynthetic- not for long ago, it was considered a
period of synthetic blank, for now to be discovered that even in G1 takes
place an intensification of the transcription and proteosythese. The most
important events that take place in this period are:
 the citokinesio`s development
 the nucleon’s biogenesis
 the chromosome` s maximum uncycling that are monochromatidical,
and the the DNA quantity =2 C
 the synthesis of every type of DNA, especially of the ribosomal
RNA
 recently it has been discovered that it synthetisized and
approximately 20-25% of hystionic proteins, that apparently are
involved in the fast neutralization of the negative loading of the
phosphate groups of the synthetisized DNA in the S period
 the replication of the centrosome in the cells where he exists, and of
the structures involved in the division spindle and also of the
organoides associated with the nucleus
 the U protein` s synthesis that starts the DNA replication in the
synthesis period.
It is the most variable period in time, occupying between 20-25%
from the interphase duration.
The S Period - the synthesis- in this period, takes place during its
whole time the nuclear
DNA replication simultaneous in all the
chromosomes and in many points, also for the hystonic proteins that form
together the cromatine fiber. The DNA quantity rises slowly from the
diploid level 2C, going through intermediate phases 2,5C , 3C, 3,5C, until it
arrives to the fourth level, 4C, whent the synthesis is done. This takes place
when the replication of all chromosomes regions from all the cells is over.
At the end of the period each chromosome is made up of two chromatides.
The period, S has a relatively constant duration for a cell and represents 3540% of the interfase. For example, for the Vicia faba it represents 6 to 8
hours out of the total 19 hours of the cellular cycle.
The G2 Period – Postsynthetic – it is the period which prepares the
mitosis through:
 the production of the molecules required by the division spindle and
the mitotic apparatus
 the synthesis of the chromosomal RNA
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
the synthesis of the non-histonic contractile proteins such as actines,
miosins and tubulins
 the synthesis of the protein kinase which plays a role in the
structurization of the chromosome through the phosphorilation of
the histonic protein H1, which leads to the apparition of the
solenoidal structure of the cromatine fiber, but also in the
phosphorilation of the molecules from the nuclear lamin’s structure
 commencing the disorganization of the nuclear lmante
Through the normal developement of the interfase, at the end of this
phase, the volume of the cell will have doubled, both through the increase of
the genetic information and through the increase of the number of cellular
organites, thus being able to enter into the cell division phase.
Cell division – represents the second important phase of the cell
cycle (and is relatively short, accounting for only about 10% of the duration
the cell cycle), considered as being the fourth stage in the cycle, during
which a series of processes take place coordinated by and which lead to the
division of the nucleus (karyokinesis) and of the cytoplasm (cytokinesis),
having the role of equally distributing the synthesized cellular components
in the interfase, between the two (mitotic division), and respectively four
cells (meiosis division) to be created.
Betula pendula is part of the spermatophyta phylum, the
angiosperms subphylum, the dicotiledonates class, fagales order, betulaceae
family. It inhabits mountainous and hillside forests, up until the subalpine
floor, reaching up to 30 m in height, with the trunk displaying a whitish soft
bark with annular exfoliation; the leaves have a rhomb or triangle ovate like
shape, sharp, with doubly serrated edges. The feminine and masculine
flowers, are arranged in a cylindrical cone type shape, and the fruits, display
a small nuculus, with wide wings.

MATERIAL AND METHOD
The biological material is represented by the germinated birch seeds,
which are used for the making of certain preparates, through which a real
mithosis can be observed, as well as to be used as biologic material by
treating them with colchicine, so as to be able to observe an abnormal
mithosis.
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
Work method:
The germinated birch seeds are inserted in a colchicine solution of
0.2%; the duration of the colchicinization being 2 to 4 hours.
The bracing of the material
After refinement, the sprouted seeds but also the ones that were not
treated with colchicine are passed through a solution of ethanol – acetic acid
3:1. The duration of the bracing is of 24 hours after which the used material
is passed through a solution of ethanol 70% being able to be preserved for a
long period of time.
The Effectuation of microscopic chemicals
The branched material is colored with a 1% carmine acetic solution
after which the seeds are passed into a test tube where they are boiled with
the dye for 5-6 min. After boiling, the dye is recovered and the seeds are
passed into a capsule containing 45% acetic acid solution for clarifying for
1-2 min. Then the microscopic chemicals are effectuated by pressing after
the squash method.
RESULTS AND DISCUSSIONS
The mitotic division (“mithos” = strand)
It is also called the homeotypical division because it starts from the
diploids cells and also arrives at them, because the mother cell conserves her
initial joint of chromosomes (insuring the balanced distribution of the
genetic information in the two cells), the daughter-cells presenting the same
number of chromosomes as the mother-cell.
Studying the formula of mitosis there can be observed that the miotic
cellular circle represents an imitable phase that takes up about 85-95% of
time and a distributive phase that takes up about 10-15% of time (1R/1D)
The mitosis is divided in the following phases: the prophase,
metaphase, anaphase and telophase during which the acts of biochemical
and morphological transformations take place and determine the
composition of two nuclei sons and the second phase called cytokinesis
which begins in the anaphase and ends at the end of the cellular circle.
Prophase – it encompasses three subphases: the early prophase,
middle prophase and late prophase.
The early prophase
After the chromosome duplication in the interphasic nucleus, takes
place their individualization, by the condensation of cromatine which
results in the formation of a lung and thin continuum filament.
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
Through condensation chromosomes became shorter and thicker
(replicated). Thus, the double structure can be observed (composed by two
cromatides binded at the centrometer and coiled one around the other)
attached on the endoplasmatic face of the interior membrane pf the nucleus.
This coiling of the chromosome is acomplished thanks to the
proteinkinaze enzyme which produces the phosphorilation of the histonic
protein 1, this thing leading to the formation of the secondary structure of
the chromosome named solenoid.
The middle prophase
In this subphase, the nucleus starts to disorganize and the edification
of the divisional spindle takes place. At the beginning of the prophase, the
centrosome (the cell center), formed of two centrioles, divides, resulting two
centrosomes. Each of them contains two centrioles, a developed one and one
in growth. The two centrosomes depart one from another in the middle
prophase to the two poles of the cell. Around each centriole fibers which
contain aster are radial disposed. In the same time, biosynthesis is being
produced by microtubules, which will form the fibers of the divisional
spindle which has a bipolar structure.
The divisional spindle is composed by two types of fiber: continuous fibers
(disposed between the two centrioles without being connected with them,
which form the central of the primal spindle) and semi-fibers (which reach
the equator, being disposed on the extremes of the divisional spindle).
The centrosome
Is typical for the animal cells, plants don’t contain it, but they do
have cytoplasmatical zones which feature functions of the organization of
the divisional spindle.
In the early and middle prophase, the synthesis of the RNA and non-histonic
contractile proteins, which contribute to the development of the
chromosome and edification of the divisional spindle, continues.



The late prophase
During this subphase, the following processes take place:
the full disorganization of the nucleus and the nuclear envelope
through the phosphorisation by the protein kinase of two from three
proteins belonging to the internal lamina
the disappearance of the nucleolus
the apparition of the kinetochores
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
The prometaphase
There are specialists who introduce between the prophase and
metaphase of the cell division one more phase called prometaphase, which
is defined by:
 the whole disappearance of the nuclear envelope
 the apparition on the kinetochore of the kinetochorical fibers of the
divisional spindle, formed by a group of microtubules which radiate
in opposite directions on the two kinetochorical regions of each
chromosome on position on the metaphasical plate, as well as during
the circulation from anaphase to centrosomes
 the continuation of the condense of the chromosomes and the
orientation regarding the poles of the divisional spindle
 the circulation of the chromosomes to the center of the cell through
disoriented movements which oscillate. It might happen that at one
point, the kinetochorical fibers on one side of the chromosome
arrange in the space between the polar fibers from a centrosome and
the other kinetochor associates with the polar fibers which leave
from the opposite centrosome.
The movement and the orientation of the chromosomes to the center
of the cell are considered to be partially influenced by the fibers of the
achromatic spindle, each chromosome acting independently from the others.
Metaphase:
In the metaphase are taking place different phenomenens:
 the development of the achromatic spindle
 the disposal of the bichromatins chromosomes in the equatorial
region of the cell,taking the shape of a ring or an equatorial plate
around the dividing spindle attached
 to the centromere with the help of the kinetochores fibres,in one
perpendicular plan on the division strand.
 the
cycling of the chromosomes continues,with maxim
condensation,which makes the individual chromosomes visible
 due to the strong condensation of the chromosomes,the metaphase
becomes inactive(inert), synteticly speaking
 at the end of the metaphase,takes place the finalization of the
reduplication of the centromeres,which leads to their longitudinal
clivation and to the separation of the sister chromatids,which
become chromosomes-sons, resulting in the doubling of the number
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of chromosomes,each chromosome being now formed of a
chromatid.Each chromatide moving in one
 of the two sister cells, which makes every sister cell to inherit the
same number of chromosomes which the cell-mom has.
The metaphase is shorter than the prophase but longer than the
anaphase.
Anaphase
The beginning of the anaphase means the endding of the complete
separation of the chromatids and the beginnig of theire journey into the
cell`s poles.The monochromathins chromosomes have a DNA quantity of
2C and undergoes a process of decondensation which leads to their increase
in lenght,but in some cases when the cycling process continues,they become
more condenseds than in the mitosis.
The shifting of the chromosomes is mainly exerted by the
kinetochores,which are the first to arrive at the poles,leaving behinde the
chromosomes arms.
At the end of the Anaphase and the beginning of the Telophase,the
chromosomes arrive to the two poles of the cells and form 2 grupes of
chromosomes-sons.
The way that chromosomes move towards the cell`s
poles,determined the arise of numerous theories,one of the most plausible
would be that the shifting implies two events:
 moving of the kinetochores fibres towards the poles pulling the
Chromatids
 the extension and sliding of the polares fibers,one on top of the
other, to drive the spindle poles further apart from eachother.
The shifting of the chromosomes towards the poles is achieved by
shortening of the spindle microtubules from the kinetochore fibers
positioned unto the centrosome.As the depolisation of the tubuline,the
kinetochore fibers become shorter and the chromosomes are pulled unto the
poles.
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STUDIA UNIVERSITATIS – Seria Ştiiţe Inginereşti şi Agro-Turism Nr. 3/2008
Fig. 2 Chromosomes in metaphase for the Betula pendula
Telophase
The chromosomes arrived at the poles of the cell as some alonged
fibers and coiled up ones around the others, which suffer reverse changes as
those from the prophase and they are:
 Decondensation and decycling which produce the loss of the
individuality and the reconstitution of the amount of
heterochromatin and euro chromatin.
 Foundation of a nucleus at the poles of each cell; for both of the two
cells that will result around the chromosomes it is going to
reorganize the cellular membrane.
 In the nucleus starts the synthesis of ARN.
Cytokinesis
The end of telophase brings to the division of the cytoplasm,
phenomenon named cytokinesis. At plants the cytokinesis involves the
foundation in the equatorial part of the mother-cell, of a separation
membrane named fragmoplast, which is found from the multiplication of the
fibers of the division spindle and the vacuolization of those at the level of
equator on account of the cytoplasm and of cellular membrane.
In case that the biologic material treated with colchicine there could
be observed fallacious pictures of the normal mitosis. In metaphase all the
chromosomes seem to be orientated to the center of the cell founding a
stellar metaphase. Beside the stellar metaphases there also appear some
other types of metaphases: the multi-stellar metaphases in which the
chromosomes present more centers of orientation, the deformed stellar
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metaphases in which the chromosomes present pictures orientated with lopsided arrangements and retards chromosomes (late), metaphases like balls in
which the chromosomes are circular arranged, they are very contracted and
they present tendencies of apparent fusion. In anaphase there were observed
semi migrations of the chromosomes to the poles of the cell, retard
chromosomes and chromatic decks which shows us the chromosomally
fallacies. In teleophase there were observed retard chromosomes or
chromosomes which form micro nucleuses.
Fig. 3 Anaphase with multiple chormatidic bridges and many late phase
chromosomes
REFERENCES
Carabas Marian,Ardelean Aurel,2005,Tehnici clasice si moderne de
evidentiere a cromozomilor la animale, Ed. "Vasile Goldis" university Press
- Arad
Carabas Marian,Ardelean Aurel,2006,Genetica lucrari practice,Ed."Vasile
Goldis" university Press - Arad
Coman N.,Dordea M.,1991,Genetica-indrumator de lucrari practice,
Ed.Universitatii, Cluj-Napoca
Gavrila Lucian si colaboratorii,2003,Genetica-vol.I,Ed.Enciclopedica,
Bucuresti
Raicu P.,1997,Genetica generala si umana,Ed.Humanitas.
Toma N.,Anghel I,1985,Citologie vegetala,Ed.Universitatii,Bucuresti.
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