A karyotype is the number and appearance of chromosomes in a cell. It depicts the complete set of chromosomes and can detect abnormalities. The study of whole chromosome sets is called karyology. Chromosomes are arranged in a standard format called a karyogram or idiogram. A karyotype is prepared by culturing cells to induce cell division, arresting mitosis, staining the chromosomes, and analyzing their number, size, shape, and banding pattern under a microscope. This allows detection of chromosomal abnormalities that can indicate genetic disorders.

1. Karyotype

2. “Karyotype”
Definition:
A karyotype is the number and
appearance of chromosome in the nucleus
of a eukaryotic cell The term is also used
for the complete set of chromosomes in a
species or in an individual organism and
for a test that detects this complement or
measures the number

3. Karyology & Idiogram
Definitions :
The study of whole sets of
chromosomes is sometimes known as
karyology.
 The chromosomes are depicted in a
standard format known as a
karyogram or idiogram

4. Explanation
In pairs, ordered by size and position of
centromere for chromosomes of the same
size.
 Derived from Greek word “karyon”, which means
"nucleus”, karyotype is represented as Idiogram.
 • When the haploid set of chromosomes of an
organism are ordered in a series of decreasing size,
it is said to be an idiogram.
 • In other sense diagrammatic representation of a
karyotype is an Idiogram.

5. Chromosome
DNA packaging into thread-like structure Is
called “chromosomes”.
Each chromosome is made up of DNA tightly
coiled many times around proteins that support
its structure.
Only visible during cell division.
It has specific number in each species e.g.
Humans have 46 chromosomes while dog has
78 & fruit fly has 8 chromosomes.

6. Centromere
Constricted region of linear chromosome is
known as “Centromere”.
Divides the chromosome in two regions
referred as “arms”.
Help to keep aligned on mitotic apparatus
during cell division
Provide a site for attachment of sister
chromatids.

8. Division of chromosome according
to centromere location
 Metacentric
 A chromosome that has a centrally placed centromere.. having
centromere in the center such that both sections are of equal length. e.g.
Human chromosome 1 – 3 & 16 – 20
 Sub metacentric
 A chromosome whose centromere is placed closer to one end than the
other having centromere slightly offset from the center leading to
asymmetry. e.g. human chromosomes from 4 – 12.
 Acrocentric
A chromosome whose centromere is placed very close to, but not at,
one end having centromere severely offset from center leading one
very long and one very short section. e.g. human chromosomes
13,15,21,22.
Telocentric :-
having centromere at very end of chromosome.
Humans don’t have this type of chromosomes but found in other
species like mice.

11. Human ideogram
 Metacentric chromosomes in human idogram are
shown in red box thy are 9 in number..
 Sub metacentric chromosome in human idogram are
shown in blue box they are 10 in number.
 Acrocentric chromosome inhuman are shown in black
colure and they are 5 in number.
 There are no telocentric chromosomes in humans

13. Preparation of chromosome for
karyotyping
Karyotyping is a process of finding a
chromosomal characteristics of a cell
Karyotyping refers to the analysis of
chromosome.
The chromosome preparation for
karyotyping is generally occur to know
about chromosome abnormalities.

14. Fig. 6-6, p. 124
Add a few
drops of blood. Add phytohemagglutinin to
stimulate mitosis.
Draw 10 to 20 ml
of blood.
Incubate at 37°C for 2
to 3 days.
Transfer to tube
containing fixative.
Transfer cells
to tube.
Add Colcemid to
culture for 1 to 2 hours
to stop mitosis in
metaphase.
Centrifuge to
concentrate cells. Add
low-salt solution to
eliminate red
blood cells and
swell lymphocytes.
Drop cells onto
microscope slide.
Examine with
microscope.
Digitized
chromosome
images processed
to make karyotype.
Stain slide
with Giemsa.

15. Analysis of karyotyping
 Karyotype can be analyzed by basic
following techniques.
 Different stains and dyes produce banding
patterns specific to each chromosome.
 And there is chromosome painting
technique as well for the analysis of
karyotyping.

16. Classification of banding
techniques

17. BANDING OF CHROMOSOMES
G - Banding
Q - Banding
C - Banding
R - Banding

19. Q-banding
1. Dehydrate the slides by dipping in alcohol
with decreasing concentration 90%, 70%
and 50% one min each.
2. Rinse in distilled water. .
3. Wash the slide in phosphate buffer at pH
6.8.
4. Stain the slide in quinacrine mustard (5 mg
in 100 mI) or in quinacrine dihydrochloride
5% for 20 min.
5. Rinse in phosphate buffer and mount in the
same buffer.
6. Examine under fluorescent microscope.

21. METHODOLOGY
G- Banding technique
Ageing of good slides for 10 days
Normal saline
Treated with trypsin 0.25% solution 10-15 sec
Immersed in 70% ethanol for few minutes
Stained with 10% Giemsa for 6-10min
Microphotograph good spreads
Construction of G-banded karyotype

23. N banding technique
 Take a chromosome from a blood sample.
 Give dry air to the chromosomes.
 Treated this dried air chromosome with 5 %
solution of
Tricholoroacetic acid 95* C for 30 min
 Treated this solution with 0.1 N of HCl at 60*C
for 30 min.
 After this the banding pattern in structural non
histone protein linked to NOR region.

25. C-banding
1. Treat the slides in 0.2 N HCI for one hr at
room temperature.
2. Rinse in de-ionized water.
3. Immerse in 1% barium hydroxide at 50°C
for 5-15 min.
4. Rinse in deionized water.
5. Incubate at 60°C in 2XSSC buffer for one hr.
6. Rinse in de-ionized water and stain in 4%
Giemsa stain for 90 min.
7. Rinse in de-ionized water, dry and examine
under oil immersion.

27. Chromosome Painting
 New techniques using fluorescent dyes generate unique
patterns for each chromosome
 Chromosome ‘painting’ refers to the hybridization of
fluorescently labeled chromosome-specific.
 Chromosome painting allows the visualization of
individual chromosomes in metaphase or interphase
cells and the identification of both numerical and
structural chromosomal aberrations in human
pathology with high sensitivity and specificity.

29. Information Obtained from a
Karyotype
 Number of chromosomes
 Sex chromosome content
 Presence or absence of individual chromosomes
 Nature and extent of large structural
abnormalities

30. Major use of Karyotyping
in Important test
 Any nucleus can be used to make karyotype
 Lymphocytes, skin cells, tumor cells
 Sampling cells before birth
 Amniocentesis
 Chorionic villus sampling (CVS)

31. Amniocentesis
A method of sampling the fluid
surrounding the developing fetus by
inserting a hollow needle and withdrawing
suspended fetal cells and fluid
Used in diagnosing fetal genetic and
developmental disorders
Usually performed in the sixteenth week of
pregnancy

33. Chorionic Villus Sampling
(CVS)
A method of sampling fetal chorionic
cells by inserting a catheter through the
vagina or abdominal wall into the
uterus
 Used in diagnosing biochemical and
cytogenetic defects in the embryo
 Usually performed in the tenth week of
pregnancy

35. CVS & Amniocentesis

36. Advantages of karyotype
 Detection of chromosomal abnormalities
 Genetic disorders
 Gender identification
 Identify loss and addition of chromosome
 Pre-birth diagnosis of genetic diseases
 Identification of chromosomal numbers in
different organism
 Identification of proper position of genes in
chromosomes

37. Disadvantages of karyotype
 Very small abnormality cannot be shown by
karyotyping.
 Technique only allows for diagnosis and not
a cure
 The test like amniocentesis and CVS are
both risky an stressful for mother
 Time consuming process
 A minor mistake in a process will change all
the result.