karyotype analysis

1. WELCOME

2. Karyotype analysis and Evolution of
Karyotypes

3. Karyotype
Definition
 A karyotype is the number and appearance of chromosomes 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 .
 The study of karyotypes is important for cell biology and genetics, and
the results may be used in evolutionary biology and medicine.

4. History of karyotype
 Chromosomes were first observed in plant cells by Carl
Wilhelm von Nageli in 1842.
 The name was coined by another German anatomist, Heinrich
von Waldeyer in 1888. It is New Latin from Ancient Greek
karyon, "kernel", "seed", or "nucleus", and typos, "general
form").
 Lev Delaunay seems to have been the first person to define
the karyotype as the phenotypic appearance of the somatic
chromosomes, in contrast to their genic contents (1922).

5. Observations on karyotypes
Staining
The study of karyotypes is made possible by staining. Usually,
a suitable dye, such as Giemsa, is applied after cells have
been arrested during cell division by a solution of colchicine
usually in metaphase or prometaphase when most
condensed.
For humans, white blood cells are used most frequently
because they are easily induced to divide and grow in tissue
culture.

6. Observations
 Six different characteristics of karyotypes are usually observed and
compared:
I. Differences in absolute sizes of chromosomes. Chromosomes can
vary in absolute size by as much as twenty-fold between genera of
the same family
II. Differences in the position of centromeres. These differences
probably came about through translocations.
III. Differences in relative size of chromosomes. These differences
probably arose from segmental interchange of unequal lengths.
IV. Differences in basic number of chromosomes.
V. Differences in number and position of satellites. Satellites are small
bodies attached to a chromosome by a thin thread.
VI. Differences in degree and distribution of heterochromatic regions.
Heterochromatin stains darker than euchromatin.

7. Variation is often found:
I. between the sexes,
II. between the germ-line and soma (between gametes and the rest of
the body),
III. between members of a population (chromosome polymorphism),
IV. in geographic specialization, and
V. in mosaics or otherwise abnormal individuals.

8. Diversity and evolution of karyotypes
Although the replication and transcription of DNA is
highly standardized in eukaryotes, the same cannot
be said for their karyotypes, which are highly
variable. There is variation between species in
chromosome number. This variation provides the
basis for a range of studies in evolutionary cytology.

9. Changes during development
Chromosome elimination. In some species, as in many
sciarid flies, entire chromosomes are eliminated during
development.
Chromatin diminution (founding father: Theodor Boveri).
In this process, found in some copepods and roundworms.
X-inactivation. The inactivation of one X chromosome
takes place during the early development of mammals.

10. Number of chromosomes in a set
The number of chromosomes in the karyotype between
(relatively) unrelated species is hugely variable.
The low record is held by the nematode Parascaris
univalens, where the haploid n = 1; and an ant: Myrmecia
pilosula
. The high record would be somewhere amongst the ferns,
with the adder's tongue fern Ophioglossum ahead with an
average of 1262 chromosomes.

11. Ploidy
Ploidy is the number of complete sets of chromosomes in a
cell.
 Polyploidy, where there are more than two sets of
homologous chromosomes in the cells, e.g.:3n, 4n etc.
 Haplo-diploidy, where one sex is diploid, and the other
haploid. It is a common arrangement in the Hymenoptera,
and in some other groups.
 Endopolyploidy occurs when in adult differentiated
tissues the cells have ceased to divide by mitosis, but the
nuclei contain more than the original somatic number of
chromosomes.

12. Aneuploidy
The number of chromosomes is not a multiple of
the normal haploid number.
Monosomy
one member of a chromosome pair is missing, (2n-1)
Trisomy
one chromosome set consists of 3 copies of a
chromosome, (2n+1)

13. Chromosome Banding
Q
(Quinarcine)
G
(Giemsa)
N (NOR)
C
(Centromeric)
1958 1971 1973 1978
Casperson
et.al
Summer
et.al
Matsui &
Sasaki
Linde
&Laursen

14. 1.Q Banding Techniques
Chromosome
Stained with Quinarcine Mustard
Subjected UV light
Banding Pattern
Region rich in GC
bases
Region Rich in AT
bases
Light stainingDark staining
GC region quenches dye but do
not fluorescence ,situated in
euchromatin region
AT region quenches dye &
fluorescence, situated in
heterochromatin region

15. 2.G Banding Techniques
Chromosome
Weak Trypsin /
urea/ protease
Treated with
Giemsa
Banding pattern
To
denature
protein
Interaction of
the DNA with
thiazine & eosin
components of
stain brightens
sulphur rich
regions
Methylene Azure+
Methylene Violet+
Methylene Blue+
Eosine

16. 3. N Banding Techniques
Chromosome
Air Dried
Treated with 5% Trichloroacetic
acid @ 95ᵒC for 30 min.
Treated with 0.1N HCl @ 60ᵒC for
30 min.
Banding pattern in Structural non-
histone proteins linked to NOR region

17. 4. C Banding Techniques
Chromosome
Treating with alkali solution
Washing with Sodium citrate @ 60ᵒC
for 30 min.
Staining with Giemsa Solution
Banding pattern at heterochromatin
region
Repeatitive DNA
renature but
unique DNA do
not renature
DNA denaturing

18. Digital karyotyping
 Digital karyotyping is a technique used to quantify
the DNA copy number on a genomic scale. Short
sequences of DNA from specific loci all over the
genome are isolated and enumerated. This method is
also known as virtual karyotyping.

19. Chromosome abnormalities
 Numerical
Extra chromosome
missing chromosomes
Structural
Translocations
Inversions
Deletions
Duplications

20. THANK YOU