Definition Centromere Particular chromosome complement of an individual or a related group of individuals, as defined by the chromosome size, morphology, and number –Karyotype. Karyotype CLASSIFICATION OF CHROMOSOMES FORKARYOTYPING Types of karyotype Asymmetric Karyotype • Show larger difference between smaller and larger chromosome in a set. • Have more acrocentric chromosomes. • Have relatively advanced feature. Symmetric Karyotype Show lesser difference between smaller and larger chromosome in a set. • Have more metacentric chromosomes. • Have no relatively advanced feature Procedure of karyotyping SPECIMENS USED Types of banding G-banding R-banding c-banding Q-banding T-banding Karyotype Detects Various Chromosome Abnormalities Aneuploidy Deletions Duplications Translocations Idiogram Advantages of Karyotyping Disadvantages:

1. S.Swetha mohan
I-M.Sc Microbiology

2. Chromosome
Sister Chromatides

3. Definition
 Centromere Particular chromosome
complement of an individual or a related
group of individuals, as defined by the
chromosome size, morphology, and
number –Karyotype.

4. General morphology
 Size of chromosome
 Position of centromere
 Presence of secondary constriction
 Size of satellite
of somatic chromosome
complement of an individual constitutes its
Karyotype.

5. Karyotype
 The complete chromosomal set of nucleus in
the cell.
 The preparation and study of
KARYOTYPES is a part of
CYTOGENETICS.
 Cytogenetics = The study of
chromosome number, structure, function,
and behavior in relation to gene inheritance,
organization and expression

6. History of karyotyping
• Grygorii Levitsky (1931) 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”.

7. Chromosome structure
 Chromosomes are composed of chromatin ,a
combination of nuclear DNA and protein.
 For KARYOTYPING cells are captured in
metaphase. A metaphase stage in mitosis at
 which the chromosomes are aligned along
the cell equator.

8. CENTROMERE
POSITIONS
Telocentric Acrocentric
Sub metacentric Metacentric

9. CLASSIFICATION OF
CHROMOSOMES FOR
KARYOTYPING
Group A: chromosomes 1,2,3
largest metacentric
and sub metacentric
Group B: chromosomes 4,5
large sub metacentric
Group C: chromosomes
6,7,8,9,10,11,12
medium sub metacentric

10. Continue…
Group D: chromosomes 13, 14, 15
medium acrocentric
Group E: chromosomes 16, 17, 18
short metacentric or sub metacentric
Group F: chromosomes 19, 20
short metacentric
Group G: chromosomes 21, 22
very short acrocentric

11. X-chromosome – SUBMETACENTRIC
Y-chromosome - AGROCENTRIC

12. The human karyotype
 The normal human karyotypes contain 22pairs
of autosomal chromosomes and one pair of sex
chromosomes.
 Normal karyotypes for females contain two X
chromosomes and are denoted 46,XX; males
have both an X and a Y chromosome denoted
46,XY.
 Any variation from the standard karyotype may
lead to developmental abnormalities.

13. Karyotype
MALE KARYOTYPE FEMALE KARYOTYPE

14. Types of karyotype
karyotype
Asymmetri
c
karyotype
Symmetric
Karyotype

15. Types of Karyotype
Asymmetric Karyotype
• Show larger difference
between smaller and
larger chromosome in a
set.
• Have more acrocentric
chromosomes.
• Have relatively
advanced feature.
Symmetric Karyotype
• Show lesser difference
between smaller and
larger chromosome in a
set.
• Have more metacentric
chromosomes.
• Have no relatively
advanced feature.

16. • In 1931 G.A. Levitzky, a Russian scientist suggested that in flowering plants
there is a predominant trend towards karyotype asymmetry. This trend has been
carefully studied in the genus Crepis of the family compositae

17. Procedure of karyotyping

18. SPECIMENS USED
Peripheral Blood
Bone Marrow
Cultured Skin Fibroblast
Amniotic Fluid

19. Types of banding
 G-banding is obtained with Giemsa stain
following digestion of chromosomes with
trypsin.
It yields a series of lightly and darkly stained
bands - the dark regions tend to be
heterochromatic, late-replicating and AT rich.
The light regions tend to be euchromatic,
early replicating and GC rich. This method
will
normally produce 300-400 bands in a normal,
human genome.

20.  R-banding is the reverse of G-banding
(the R stands for "reverse"). The dark
regions are euchromatic (guanine-cytosine
rich regions) and the bright regions are
heterochromatic (thymine adenine rich
regions).
 C-banding: Giemsa binds to constitutive
heterochromatin, so it stains centromeres.

22.  Q-banding is a fluorescent pattern obtained
using quinacrine for staining. Barium
hydraoxide will be used. The pattern of
bands is very similar to that seen in G-
banding.
 T-banding: visualize telomeres.
 Silver staining: Silver nitrate is using for
staining

23. Fluorochrome Binding Mode Mechanism of
Banding
Selectivity
Quinacrine Intercalation AT
Daunomycin INtercalation Differential
binding
AT
DAPI AT A3 Minor groove AT
Hoechst 33258 Minor groove Differential
binding
AT
Chromomycin Minor groove GC

24. FISH

25. Karyotype Detects Various
Chromosome Abnormalities
• Aneuploidy- to many or to few
chromosomes – Trisomy, Monosomy,
etc.
• Deletions – missing part of a
chromosome – Partial monosomy
• Duplications – extra parts of
chromosomes – Partial trisomy
• Translocations – Balanced or unbalanced

26. Trisomy 21
 Abnormality
shown in
karyotype
 Note that there
are three copies
of #21
chromosome.
 This person has
Down Syndrome.

27. Turner syndrome
 Abnormality shown
in karyotype
 Note this person
only has 1 copy of
the X chromosome.
 This female has
Turner’s syndrome.

28. Klinefelter syndrome

29. Deletion (partial
monosomy)

30. Duplication (partial trisomy)

31. Translocation

32. Idiogram
 Diagrammatic representation of the gametic
chromosome set (n) of a species.
 Used to compare the karyotype of one
species with the other.
 Karyotype is represented diagrammatically
showing all the morphological features of
chromosomes.

33. Idiogram picture

35. 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.

36. Disadvantages:
 Very small abnormality cannot be shown
by karyotyping. Method of FISH is
required.
 An unknown (marker) chromosome
cannot be identified by karyotyping.