Karyotype &idiogram

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 FOR�KARYOTYPING
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. K aryotype &idiogram 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 Asymmetric 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 .

21. 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

22. 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

23. FISH

24. 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

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

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

27. Klinefelter syndrome

28. Deletion (partial monosomy )

29. Duplication (partial trisomy)

30. Translocation

31. 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 .

32. Idiogram picture

33. 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 .

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