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.
7.
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.
9.
10.
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
12.
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.
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.
20.
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
22.
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.
24.
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.
26.
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.
28.
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
32.
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
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.