A karyotype is the number and appearance of chromosomes in a cell and can provide information about an organism's species. Key features used to characterize karyotypes include chromosome size, centromere position, and banding patterns. Karyotypes can be symmetric or asymmetric and are often represented visually using idiograms or karyograms. Analysis techniques like G-banding stain chromosomes to reveal identifying patterns. Comparing karyotypes across species provides insights into evolutionary mechanisms like centric fusion and fission that alter chromosome counts. In primates, chromosomal changes like the fusion that formed human chromosome 2 are important in lineage evolution.

2. Karyotype
 A karyotype is the number and appearance of
chromosomes in the nucleus of a eukaryotic cell.
Karyotype
 Size of chromosome
 Position of centromere
 Presence of secondary constriction
 Size of satellite

3. Each group of plants or animals of species has a
set of chromosome with characteristic feature as
size , shape, position of centromere etc.
The karyotype is represented by a diagram called
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

5. Types of Karyotype
Symmetric Asymmetric

6. Types of Karyotype
Asymmetric Karyotype Symmetric Karyotype
• Show larger difference
between smaller and larger
chromosome in a set.
 Have more acrocentric
chromosomes.
 Have relatively advanced
feature
 Example- Ginkgo biloba,
flowering plants
 Show lesser difference
between smaller and larger
chromosome in a set.
 Have more metacentric
chromosomes.
 Have no relatively advanced
feature
 Example- Pinus

7. Karyotype Analysis
To determine the karyotype of an organism there are
following steps
 Collection of cell from an organism
 Induce the cell to divide
 stop cell division at metaphase
 Stain the chromosome
 Study and analyze

8.  The study of karyotype is called Karyology.
Three types techniques are used in karyotype
1. Classical karyotype analysis
2. Spectral karyotype
3. Formation of idiogram or karyogram

9. Classical Karyotype analysis
A dye Giemsa is used to stain banding pattern on
chromosomes. Also called GC- bands
Each chromosome has a specific banding pattern so
bands help in identification of chromosomes.
The chromosomes of one pair must have same pattern.

10. Spectral karyotype
This technique is used to visualize all the 23 pairs of
human chromosomes in different colours.
This technique is widely used to identify structural
chromosomal aberrations in cancer and other diseases.

11. Formation of Karyogram
This technique is used to determine diploid number of
chromosomes of an organism.
In this cells are locked in metaphase with colchicine
then stained and photographed.
They are arranged in a karyotype and karyogram.
In human female out of 2 X chromosome one remain
inactive and seem as bar body under microscope

12. Analysis of Human Karyotype
22 pairs of autosomes are arranged in 7 groups (A-G)
with different morphology.

14. Advantages of Karyotyping
Reveals structural features of each chromosomes.
 Helps in studying chromosome banding pattern.
 Helps in the identification of chromosomal
aberrations.
 Diagnosis of prenatal genetic defects.
Aids in studying evolutionary changes

15. Chromosome Banding

16. Classification of Banding Techniques
Based on
 GC and AT rich regions
 Constitutive heterochromatin region
The bands can be detected after treatment of
chromosomes with restriction enzyme(RI) so
also called- RE bands.
In chromosome banding we stain the
chromosome with different stains and study the
banding pattern.

17. Banding Techniques
G- Banding (Giemsa banding)
 R- Banding ( Reverse banding)
C- Banding ( Constitutive heterochromatin)
N- Banding ( NOR)
T- Banding (Telomeric Regions)
Q- banding (Quinarcine Banding)

18. G- Banding
Chromosome
Trypsin
Treated with
Giemsa
Banding
Partially
digest

19. The heterochromatin region which are rich in A-T base pair
stain more darkly in G-Banding while Euchromatin which is
rich in G-C bands incorporate less stain.
The bands are same in homologous chromosome so
identification become easy .
Use to identify different chromosomal abnormalities as
chromosome number, deletion, inversion etc.

20. R- Banding
Chromosome
Incubated
Treated with
Giemsa
Banding
Hot Phosphate
buffer at 86-87
°C ( 10mins)

21. R-Banding is reverse of G-Banding that is light banded
region of G banded chromosomes become lightly stained
or vice versa.
R bands are produced in G-C chromosomes.
R- banding is not observed in plant chromosomes.
A-T regions are selectively denatured by heat leaving
G-C region intact
Helpful in analyzing the structure of chromosome ends
which are usually light stained with G band

22. C- Banding
Chromosome
Treated with alkali
solution
Washed with
sodium citrate at
60°C
Stained with
Giemsa solution
DNA
Denaturing

23. C-Banding stains areas of heterochromatin which are
tightly packed and have repetitive DNA.
Useful in humans to stain centromere regions and other
regions containing constitutive heterochromatin as
secondary constriction and distal segment of Y
Chromosome long arm.
C-banding also studied in Vicia faba, Hordeum vulgare
etc.

24. N-Banding
Chromosome
Silver Nitrate
Banding in
NOR region

25. N- Banding is used to find out location of NOR
(Nucleolar Organizer Region).
Banding involves staining with silver nitrate solution to
stain NOR rich in rRNA genes.
These bands are localized in the satellites of
chromosomes.

26. T-Banding
Chromosome
Denaturation
Treated with
Giemsa
Banding

27. T-Banding involves staining of Telomeric regions of
chromosomes.
T- Bands are smaller than R-Bands.
T-Bands are strictly observed at Telomeric site

28. Q-Banding
Chromosome
Stained with
Quinarcine mustard
UV Light
Banding Pattern
Dark staining Light staining
AT region quenches dye &
fluorescence , in
heterochromatin region
GC region quenches dye
but do not fluorescence,
in Euchromatin region
Region
rich in
AT
bases
Region
rich in
GC
bases

29. Q bands are especially useful for distinguishing human Y
Chromosomes.
To identify the heterochromatin rich regions involving
satellites and centromere of specific chromosomes.

31. Karyotype Evolution
Study of Karyotypes of different species has revealed interesting
facts about both the plants and animal kingdom.
Reptiles and birds have large chromosomes
(Macrochromosomes) & small chromosomes
(Microchromosomes) that serve to differentiate them
cytogenetically.
Matthey distinguished between the basic chromosome number &
the number of chromosome arm, also called as Fundamental
number (FN). According to this concept, the metacentric
chromosome as two arms and the acrocentric chromosome and
telocentric chromosome has one arm. The number of arms in each
of different species can be compared .

32. With regard to absolute size of their chromosomes
mammals & birds constitute two independent groups. The
two orders have different DNA contents and different sex
determining mechanisms.
Two opposite changes in the number of chromosomes are
of particular importance in the evolution:-
In centric fusion, a process leads to decrease in
chromosome no. two acentric chromosomes join together
to produce a metacentric chromosome.
In dissociation/ fission, a process that leads to an increase
in chromosome no. a metacentric and a small
supernumerary metacentric chromosome become
translocated, so that acrocentric and submetacentric
chromosome are produced.

33. Fusion and dissociation/fission are the main mechanism by
which the chromosome no. can be decreased or increased
during evolution of the majority of animals and in some
group of plants.
Observations of chromosomal organization and of the
different Karyotypes in the individual the species, the
genes, and the major systematic groups indicates that a
chromosome mechanism are involved in evolution.
Evolution , however is a very complex and should be
considered different from different biochemical,
cytological, genetic, ecological and experimental aspects.

34. Karyotype Evolution in Primates
In recent years a great deal of work on evolutions has
focused on the possible cytogenetic relationship
between great apes and human species.
It was found that the primates have 48 chromosomes
and attempts were made to correlate the 24
chromosome pair with 23 pairs in humans. This
analysis was greatly facilitated by the use of banding
techniques that allow one to study the inner structure
of each chromosomes.

35. These comparative studies have been demonstrated:-
 13 pairs of chromosomes in humans are identical with 13
pairs of chimpanzee.
 Chromosome no.2 in humans has resulted from centric
fusion of two chromosomes present in hominoid apes.
 The other chromosomes differ in occurrence of nine
pericentric inversion and two additions of chromatin
material.
The karyotype evolution in primates consists of the
modification of the morphology in the form of fusion,
fission, inversion,& reciprocal translocation.

36. At present, pericentric inversion appears to be main
structural difference between individual chromosome
of great apes & humans.
It has been postulated that evolution of human
karyotype has occurred by series of pericentric
inversions which permitted the genetic isolation of
small breeding groups and selection of favorable gene
combination that give rise to homosapiens.