karyotyping and cell division.ppt..

DR. ASHISH PATEL
Assistant professor
Dept. AGB, Veterinary College,
AAU, Anand

Karyotype is a complete set of metaphase
chromosomes arranged in pairs, on the basis of size,
centromere position and shape.
In a karyotype, chromosomes are arranged and
numbered by size from largest to smallest.
This arrangement helps in quickly identify
chromosomal alterations that may result in a genetic
disorder.

For making karyotype, to take the picture of
chromosome, cut and match every chromosomes on
the basis of size, banding pattern and centromere
position.
Avian karyotype is different from mammalian
karyotype because of presence of very small
autosomes called microchromosomes.

Use of KaryotypingUse of Karyotyping
It permits an accurate count and characterization of
chromosomes of an individual/species
It permits rapid identification of chromosomal
abnormalities, particularly those involving structural
changes
IdiogramIdiogram
Idiogram is the diagrammatically representation of the
chromosomes arranged in descending order of length. Or
The karyotype can be represented diagrammatically with
all the morphological features of chromosomes, such a
diagram is known as idiotype.

6
CELL PREPARATION
Culture cells until sufficient mitotic activity
Add colchicine to arrest in metaphase
Add hypotonic salt solution to swell cells
Fix with mix of methanol: acetic acid

Normal karyotype of cattle
[2N = 60, XY]
7

8
Karyotypes of Murrah buffalo, an Indian
dairy breed [2n=50]
Karyotypes of Asiatic swamp buffalo
in Thailand [2n=48]

NORMAL KARYOTYPE of DOG
[2N = 78,XY]
All autosomes are acrocentric
The sex-chromosomes are metacentric

10
NORMAL KARYOTYPE of CAT
[2N = 38,XY]
They are all metacentric

NORMAL KARYOTYPE of SWINE
[2N=38,XX]
Swine have 6 pairs of acrocentric chromosomes and 12 pairs of
metacentric autosomes.
The X-chromosomes are also metacentric.
11

12
The horse has 18 pairs of acrocentric and 13 pairs of metacentric
autosomes, the X- and Y-chromosomes are also metacentric.
NORMAL KARYOTYPE of HORSE
[2N= 64,XX]

13
The ass has 62 chromosomes which are quite different from the
ones of the horse. The mule is an infertile cross between the
horse and the ass.
NORMAL KARYOTYPE of ASS
[2N= 62,XX]

Chromosomal BandingChromosomal Banding
 It is process, in which chemical treatment given to
metaphase chromosomes and which would be visible
in alternative lighter and darker band.
Various types of bandings are:
G – banding
C – banding
Q – banding
R - banding
T – banding
NOR - banding

Lampbrush chromosomesLampbrush chromosomes
It was first observed by W. Flemming in 1882.
It consists of an axis from which paired loops extend in
opposite directions, giving the appearance of a lamp
brush. Hence the name Lamp Brush Chromosomes.
It is found in the Oocytes of amphibians and in some
insects.
It is larger in size, So it is called a giant chromosome.

Holocentric chromosomesHolocentric chromosomes
The chromosomes with a non-localized centromere
are called as either holocentric or holokinetic
chromosomes

Species 2n Autosomes X
Chromosome
Y Chromosome
Sm/ m A
Swamp Buffalo 48 10 36 A A
River Buffalo 50 10 38 A A
Zebu Cattle 60 - 58 Sm Sm
Exotic Cattle 60 - 58 Sm A
Sheep 54 6 46 A Sm
Goat 60 - 58 A Sm
Pig 38 24 12 Sm m
Dog 78 - 76 Sm Sm
Horse 64 26 36 Sm m
Donkey 62 38 22 Sm m
Chromosome number and morphology in some species of animals:

The division of chromosome and cytoplasm of a cell
into two daughter cells is known as cell division.
The cell cycle or cell-division cycle is an ordered
series of events that take place in a cell leading to cell
growth and its division and duplication (replication
into two daughter cells).
Cytokinesis is the physical division of the cytoplasm
whereby the nuclei, cytoplasm, organelles and cell
membrane of a single eukaryotic cell is divided into
two daughter cells containing roughly equal shares.

There are mainly two types of cell division:
(1)Mitosis
(2)Meiosis.
The various events occurring during cell division may
be grouped in to two categories:
(1)Karyokinesis
(2)Cytokinesis.
Karyokinesis is the division of chromosome of a cell in
to two daughter nuclei.
Cytokinesis is the division of cell in to two halves to
produce two daughter cells. (As a rule, Cytokinesis
follows Karyokinesis).

Types of Cell DivisionTypes of Cell Division
MitosisMitosis
The mitotic cell division was first described by Flemming in
1879.
Somatic cells of all organisms divide through mitosis.
Mitosis produces two daughter cells that are identical to the
parent cell.
This type of cell division allows organisms (multicellular) to
grow and repair damaged tissue.
MeiosisMeiosis
Meiosis (double cell division) produces daughter cells that have
one half the number of chromosomes as the parent cell.
Meiosis is necessary in sexually-reproducing organisms because
the fusion of two gametes (fertilization) leads to doubles the
number of chromosomes.

MITOSISMITOSIS
Mitosis is a process of nuclear (karyokinesis) and
cytoplasmic (cytokinesis) division in which two
daughter cells are produced that has chromosomal
numbers identical to the parental cell.
Mitosis (M Phase) is part of the total cell cycle for
cells undergoing division.
The initial event in the cell cycle is the growth phase,
called Interphase.

INTERPHASEINTERPHASE
The interphase is much longer phase of cell cycle,
where the cell prepares itself for cell division.
Interphase is divided into three phases:
G1 (first gap)
S (synthesis)
G2 (second gap)
During all three phases of Interphase, the cell grows
and engaged in high metabolic activity to prepare its for
mitosis.

G1 PHASEG1 PHASE
In this phase, the cell increases in mass and prepares for DNA replication.
The metabolic rate of the cell will be high.
It takes about 10 hours.
S PHASES PHASE
DNA replication.
Cells will take 5 to 6 hours to complete S phase.
G2 PHASEG2 PHASE
The cell undergoes of rapid growth to prepare for mitosis.
G2 is shortest subphase of interphase and it lasting only 3 to 4 hours.
G2 phase is after DNA synthesis but prior to the start of prophase of
mitosis.

STAGES OF MITOSISSTAGES OF MITOSIS
Mitosis is divided into,
Prophase
Metaphase
Anaphase and
Telophase

The first phase of mitosis.
Chromosomes become
condenses and each
chromosome has two
chromatids joined at a
centromere.
The mitotic spindle initially
appears as structures called
asters which surround each
centriole pair.
The two pair of centrioles move
away from one another toward
opposite ends.
ProphaseProphase

MetaphaseSpindle fibers attached to all
chromosomes at the
kinetochore(centromere
region on the chromosomes
where sister chromatids are
joined) .
The chromosomes begin to
migrate towards the center of
cell.
The condense chromosomes
arrange in a line near the
center of the cell, that position
is called as Equatorial plane or
Metaphase plate

The nuclear membrane
disappears completely.
Chromosomes align at the
metaphase plate (equatorial
plate) at right angles to the
spindle poles.

AnaphaseSpindle fibers shorten, the
kinetochores separate and
centromeres of each
chromosome begin to move
apart to the cell poles.
Once the paired sister
chromatids separate from
one another, each is
considered a "full"
chromosome (daughter
chromosomes).

Through the spindle
apparatus, the daughter
chromosomes move to the
poles at opposite ends of
the cell.
At the end of anaphase,
each pole contains a
complete compilation of
chromosomes.

TelophaseTelophase is last phase of
mitosis. (Latin word telos
which means 'end‘).
The daughter chromosomes
arrive at the poles and
nucleus begin to form at
opposite poles.
The nuclear envelopes of
these nuclei are re- formed
and reappear.
Nucleolus also reappear.

Chromatin fibers of
chromosomes uncoil.
The spindle fibers also
disappear.
The chromosomes
begin to decondense
and become more
diffuse.

CYTOKINESISCytokinesis is the division of
the cell's cytoplasm and
organelles.
With the two nucleus at
opposite poles of the cell, the
cell cytoplasm separates,
ultimately leading to
cleavage.
At the end of cytokinesis,
there are genetically
identical two daughter cells.

Time Duration
18-24 hours at 37 °C temperature
95 % time during interphase and only 5 % during
mitosis
Among mitosis: prophase takes 40 -50 % of total time
Anaphase is shortest in duration.

Leland H. (Lee) Hartwell, Tim Hunt and Sir Paul
M. Nurse were awarded the Nobel Prize in
Physiology or Medicine in 2001 for their
discoveries of key regulators of the cell cycle.

karyotyping and cell division.ppt..

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