INTRODUCTION WHAT IS MITOSIS PHASES OF CELL CYCLE AND MITOSIS SOURCE & REASON OF ABNORMAL MITOSIS EFFECTS OF ABNORMAL MITOSIS ABNORMALITIES OF MITOSIS IN PLANTS ABNORMALITIES OF MITOSIS IN ANIMALS & HUMAN BEINGS FACTORS RESPONSIBLE FOR MITOTIC ABNORMALITY ADVANTAGES & DISADVANTAGES OF ABNORMAL MITOSIS CONCLUSION REFERENCE

1. Abnormalities in Mitosis
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPSIS
1.INTRODUCTION
2.WHAT IS MITOSIS
3.PHASES OF CELL CYCLE AND MITOSIS
4.SOURCE & REASON OF ABNORMAL MITOSIS
5.EFFECTS OF ABNORMAL MITOSIS
6.ABNORMALITIES OF MITOSIS IN PLANTS
7.ABNORMALITIES OF MITOSIS IN ANIMALS & HUMAN
BEINGS
8. FACTORS RESPONSIBLE FOR MITOTIC ABNORMALITY
9.ADVANTAGES & DISADVANTAGES OF ABNORMAL
MITOSIS
10.CONCLUSION
11.REFERENCE

3. What is MITOSIS ?
THE PROCESS BY WHICH TWO
NEW NUCLEII ARE FORMED,
PRECEDING CELL DIVISION.
http://fairmanstudios.com/als.htm

4. Mitosis is the process by which a eukaryotic cell
separates the chromosomes in its cell nucleus into two
identical sets in two nuclei.
It is generally followed immediately by cytokinesis, which
divides the nuclei, cytoplasm, organelles and cell
membrane into two cells containing roughly equal shares
of these cellular components.
Mitosis and cytokinesis together define the mitotic (M)
phase of the cell cycle—the division of the mother cell
into two daughter cells, genetically identical to each other
and to their parent cell.

5. Phases of cell cycle and
mitosis
Interphase
The mitotic phase is a relatively short period of the cell
cycle. It alternates with the much longer interphase,
where the cell prepares itself for cell division. Interphase
is divided into three phases, G1 (first gap), S (synthesis),
and G2 (second gap). During all three phases, the cell
grows by producing proteins and cytoplasmic
organelles. However, chromosomes are replicated only
during the S phase.
Preprophase
In plant cells only, prophase is preceded by a pre-
prophase stage. In highly vacuolated plant cells, the
nucleus has to migrate into the center of the cell before
mitosis can begin. This is achieved through the
formation of a phragmosome, a transverse sheet of

6. The cells of higher plants (such as the flowering
plants) lack centrioles; instead, microtubules form a
spindle on the surface of the nucleus and are then
organized into a spindle by the chromosomes
themselves, after the nuclear membrane breaks
down.The preprophase band disappears during
nuclear envelope disassembly and spindle formation
in prometaphase.
Prophase: The two round objects
above the nucleus are the
centrosomes. The chromatin has
condensed.

7. Prometaphase: The nuclear membrane has
degraded, and microtubules have invaded the
nuclear space. These microtubules can attach
to kinetochores or they can interact with
opposing microtubules.
Metaphase: The chromosomes have
aligned at the metaphase plate.
Early anaphase: The kinetochore
microtubules shorten.

8. Telophase: The decondensing chromosomes
are surrounded by nuclear membranes.
Cytokinesis has already begun; the pinched
area is known as the cleavage furrow.
Cytokinesis
Cytokinesis is often mistakenly thought to be the final
part of telophase; however, cytokinesis is a separate
process that begins at the same time as telophase.
Cytokinesis is technically not even a phase of mitosis,
but rather a separate process, necessary for completing
cell division.

9. Significance of mitosis
 Mitosis is important for the maintenance of
the chromosomal set.
 Development and growth: The number of
cells within an organism increase by
mitosis. This is the basis of the
development of a multicellular body from a
single cell i.e., zygote.
 Cell Replacement: In some parts of body,
e.g. skin and digestive tract, cells are
constantly sloughed off and replaced by
new ones. New cells are formed by mitosis

10.  Regeneration: Some organisms can
regenerate their parts of bodies. The
production of new cells is achieved by
mitosis. For example; sea star regenerates
its lost arm through mitosis.
 Asexual Reproduction: Some organisms
produce genetically similar offspring
through asexual reproduction. For example;
hydra reproduces asexually by budding.
The cells at the surface of hydra undergo
mitosis and form a mass called bud. Mitosis
continues in the cells of bud and it grows
into a new individual.

11. SOURCE AND REASON OF
ABNORMAL MITOSIS
 ENDOMITOSIS(ENDODUPLICATION)
 Chromosomes replicate without subsequent
nuclear division.
 As a result the number of chromosome sets or
genome increases.
 This is similar to polyploidy and is therefore also
called Endopoloidy.
 It increases number of genes performing any
function.
 In human body, endomitosis occur in liver cells,
which have 4n and 8n chromosome number.

12. Free nuclear division
 Sometime , repeated mitosis occurs without
subsequent cytokinesis.
 It produces multinucleate condition called
Coenocyte, plasmodium or syncytium, e.g.
Rhizopus , vaucheria , slime moulds , opalina.
Tumours
 Reapeted cell division not followed by
differentiation can lead to callus or tumour
formation, i.e, an unorganised mass of cells .
 This can lead to cancer.

13. EFFECTS OF MITOTIC ABNORMALITY
 Although errors in mitosis are rare, the process may
go wrong, especially during early cellular divisions
in the zygote.
 Mitotic errors can be especially dangerous to the
organism because future offspring from this parent
cell will carry the same disorder.
 In non-disjunction, a chromosome may fail to
separate during anaphase. One daughter cell will
receive both sister chromosomes and the other will
receive none.
 This results in the former cell having three
chromosomes containing the same genes (two
sisters and a homologue), a condition known as
trisomy, and the latter cell having only one
chromosome (the homologous chromosome), a
condition as monosomy.

14. Abnormalities of mitosis in plants
Mitotic abnormality were studied in species of
Nicotiana, solanum, hyoscyanus, physalis,
lycopersicon and petunia infected with tobacco
mosaic or aspermy virus.
The abnormality ranged from persistance of the
nucleolar material untill early anaphase in all the
species examined to complete amitosis in stem
enations of petunia violacea.
The virus particle, multiplying within dividing cells,
compete with the nuclear DNA for the RNA supply in
the nucleolus.

15. Abnormality of Mitosis in Animals &
Humanbeings
 All structural abnormality are produced following
chromosome breakage.
 Chromosome breakage occurs spontaneosly in a
low frequency in almost all the tissues studied.
 Several factors that are suggested for abnormality
are cosmic radiation, nutritional deficiencies and
environmental factors (for ex. Temperature).
 Frequency of spontaneous chromosome breakage
is modified by several factors viz. age, oxygen
availability, temperature and the metabolic stage of
cell.

16. FACTORS RESPONSIBLE FOR
MITOTIC ABNORMALITIES
Two factors responsible for mitotic abnormality
I. Structural Abnormality – This abnormality
briengs about change in structure of
chromosome. All structural aberration are
produced following chromosome
breakage.Chromosome breakage occurs
spontaneously.This include ;
i. Non – disjunction
ii. Deletion
iii. Duplication
iv. Invertion
v. Translocation

17. Non- Disjunction
 When the sister fail to separate.
 One cell is given three copies (trisomy) of a
chromosome while the other gets only one
(monosomy).
 These cells are called aneploidy, and they can
cause cancer.

18. Deletion
 Sometimes during mitosis the chromosome can be
damaged.
 If the chromosome gets broken the fragement can
be lost.
 If this happen the genetic material they contain is
deleted.
 Loss of chromosome segment is known as
Deletion.
 Deletion is found in prokaryotes as well e.g.
E.coli,phage T4 etc.
 A specific deletion in chromosome 22 produces a
chromosome called “Philadelphia 22” it is
associated with chronic myelogenous leukemia.

19.  Another deficiency in chromosome 5 produces
“cry-du-chat” cry of cat syndrome.
 Individual suffering from this syndrome produce a
characteristic mewing catlike cry during childhood.
Deletion on a chromosome

20. Duplication
The presence of an additional chromosome as
compared to that normally present in the nucleus is
known as Duplication.
Origin of duplication involves chromosome breakage
and reunion of a chromosome segment with its
homologous chromosome.
Ohno (1970)has postulated that the increase in DNA
content per cell accompanying evolution and the origin
of new genes with distinct function are solely due to
Duplication.

21. Schematic of a region of a chromosome
before and after a duplication event

22. Inversion
When a segment of a chromosome is oriented in the
reverse direction such a segment is called to be
inverted and the phenomenon is termed as Inversion.
The gene sequence in the inverted segment is
exactly the opposite of that in normal homologous
segment.
The existance of inversion was first detected by
Sturtevant and Plunkett in 1926.

23. 
kmx
 Inversion that involve the centromere are called Pericentric
Inversion.
 Inversion that doesnot involve the centromere are called
Paracentric Inversion.

24. Translocation
Integration of a chromosome segment into a non-
homologous chromosome is known as translocation.
In simple translocation, terminal segment of a
chromosome is integrated at one end of non-
homologous chromosome.
The phenomenon of translocation was first
discovered in 1923 by Bridges. In Drosophila through
genetic analysis of a shift of a segment from
chromosome 2 into chromosome 3.

25. Nsa
Chromosomal translocation of the 4th & 20th Chromosome.

26. Numeral abnormality – this abnormality briengs about
change in the number of chromosome (chromosomal
abberation). This include;
 Aneuploidy
 Monosomy
 Trisomy
 Down syndrome
 Sex chromosome abnormality.

27. Aneuploidy
 The loss or gain of one or few chromosome as
compared to the somatic chromosome number of a
species is known as Aneuploidy.
 Aneuploidy changes in chromosome number do
not involve the whole genome ; they involve only
one or a few chromosome of the genome.
 The discovery of aneuploidy was 1916 when
Bridges discovered X0 male and XXY female
Drosophila which had 7 & 9 chromosome
respectively ,in place of normal 8.

28. trisomy
2n+1
Nondisjunction
 Baby has wrong chromosome number
◦ trisomy
 cells have 3 copies of a chromosome
◦ monosomy
 cells have only 1 copy of a chromosome
n+1 n
monosomy
2n-1
n-1 n

29. Monosomy
 In monosomic condition one chromosome is
missing from the somatic chromosome
complement.
 This condition is represented as 2n-1.
 Monosomics of polyploid species e.g. Wheat ,
cotton , oats and tobacco ,however are fully viable.
 A complete set of monosomics is available in these
crops.

30. Turner syndrome
 Monosomy X or X0
◦ 1 in every 5000 births
◦ varied degree of effects
◦ webbed neck
◦ short stature
◦ sterile

31. Trisomy 16 & Trisomy
Syndrome.
Trisomy
When somatic cell of an organism
contain three copies of any one
chromosome of haploid complement
,then this is known as trisomy.
It is denoted by 2n+1.

32. Down syndrome
 Trisomy 21
◦ 3 copies of chromosome 21
◦ 1 in 700 children born in U.S.
 Chromosome 21 is the
smallest human chromosome
◦ but still severe effects
 Frequency of Down
syndrome is related to
the age of the mother

33. Down syndrome & age of mother
Mother’s age
Incidence of
Down Syndrome
Under 30 <1 in 1000
30 1 in 900
35 1 in 400
36 1 in 300
37 1 in 230
38 1 in 180
39 1 in 135
40 1 in 105
42 1 in 60
44 1 in 35
46 1 in 20
48 1 in 16
49 1 in 12
Rate of miscarriage due to
amniocentesis:
 1970s data
0.5%, or 1 in 200
pregnancies
 2006 data
<0.1%, or 1 in 1600
pregnancies

34. Sex chromosomes
abnormalities
 Human development more tolerant of
wrong numbers in sex chromosome
 But produces a variety of distinct
syndromes in humans
◦ XXY = Klinefelter’s syndrome male
◦ XXX = Trisomy X female
◦ XYY = Jacob’s syndrome male
◦ XO = Turner syndrome female

35.  XXY male
 one in every 2000 live births
◦ have male sex organs, but are
sterile
◦ feminine characteristics
 some breast development
 lack of facial hair
◦ tall
◦ normal intelligence
Klinefelter’s syndrome

36. Jacob’s syndrome male
 XYY Males
◦ 1 in 1000 live male
births
◦ extra Y chromosome
◦ slightly taller than
average
◦ more active
◦ normal intelligence, slight learning disabilities
◦ delayed emotional immaturity
◦ normal sexual development

37. Some other factors responsible for
abnormality in mitosis.
Chromosome breakage is induced in a relatively high
frequency by several physical and chemical
agents.
1. Physical agent – several radiation are responsible
for chromosome breakage such as X-rays,
gamma rays, alfa rays , beta rays, neutrons etc.
2. Chemical agent – certain chemicals that are
responsible for abnormality are alkylating agents,
e.g, ethylmethane sulphonate, Ethylene-
diaminetetraacetic acid (EDTA),
ribonucleoprotein, base analogues, many
insecticides, herbicides and fungicides etc.
 Beside this certain virus e.g, measles virus and
certain genes e.g, Ac-Ds of maize are responsible

38. Advantages and disadvantages of
abnormal mitosis.
Advantage –
 We can apply this for the improvement of
crops(transgenic plants).
 The application of hairy root disease to produce
secondary metabolite.
Disadvantages –
 Many diseases arises from abnormality such as
Down syndrome, Turner syndrome, sex
chromosome abnormality.
 Which has a direct effect on phenotype and
genotype.

39. Conclution
 From above studies it is concluded that due to certain
agents the regular process of mitosis is altered refered to
as abnormal mitosis.
 This abnormal mitosis lead to changes in the genotype
and phenotype of the organism.
 The abnormality in mitosis results in variation.
 The mitotic abnormality occasionally induce spontaneous
(without any known causal factor) variation in
chromosome number or structure.
 Mitotic abnormality cause various diseases like Down
Syndrome, Turners syndrome, Jacobs syndrome.
 However it also have certain advantage like transgenic
plants(for the improvement of crops) , Transformation
(Hairy root disease).

40. Refrence
 Biology – Aasha Pillai – C.S.Mishra.
 Ravindra Nath – An Introduction to cell biology.
 A Text book of Biotechnology Genitics.
 Microbiology – Michael J Pelezar , JR E.C.S Chah ,
Noel R.KRIEG.
 WWW.GOOGLE.COM.