1. Chromosomal
Aberrations
DR.KIRTI SOLANKE
1

2. Types of Chromosomes 2

3. Types of chromosomal
aberrations/ abnormalities
NUMERICAL STRUCTURAL
• ANEUPLOIDY • Translocations
• POLYPLOIDY • Deletions
• Insertions
• Inversions
• Rings,
Isochromosomes
• Different cell lines
(mixoploidy)
• Mosaicism
• Chimerism

4. Discuss mechanism of anomaly

5. Discuss mechanism of anomaly

6. Numerical Abnormalities
• Trisomy 21: Down’s Syndrome (47,XX + 21)
• Trisomy 18: Edward’s Syndrome (47,XY + 18)
• Trisomy 13: Patau’s Syndrome (47,XY + 13)
• Trisomy of Sex Chromosome : Klinefelter
Syndrome (47, XXY)
• Trisomy X: Triple X Syndrome (47, XXX)
• Other Trisomies : Usually not viable.
• Monosomy X: Turner Syndrome (45, XO)
• Autosomal Monosomies : Not viable

10. Trisomy 21; Down Syndrome
Causes-trisomy,translocation,mosaicism
• over 60% of conceptions aborted
spontaneously
• 20% stillborn
• incidence increases sharply w/
maternal age
• 1/300 for 35 year olds
• 1/22 for 45 year olds

13. Brushfield spots on
iris
Hypotonia of
muscles

14. Simian Crease

15. TURNER’S SYNDROME 45XO
• Causes:
– Non-dysjunjtion
– Mosaicism
– Ring Chromosome
– Deletion
– Isochromosome
• Short stature
• Widely spaced
nipples
• Carrying angle at
elbow

16. Klinefelter's Syndrome (47, XXY)

20. STRUCTURAL ABERRATIONS
20

21. Structural Abnormalities Of
Chromosomes
• Result from the breaks in the chromosomes
• Causative factors for the breaks:
• Radiation, Drugs ,Viruses.
• Types of structural abnormalities are:
1. Deletion
2. Insertion
3. Duplication
4. Inversion
5. Isochromosome
6. Translocation
7. Transposition
8. Ring Chromosome
21

22. Structural Abnormalities Of Chromosomes
• Classified as
– Stable & Unstable
• Also classified as
– Balanced & Unbalanced
22

23. Terminal Deletion
23

24. Interstitial Deletion
24

25. Interstitial Deletion
25

26. Deletions
• May arise through
unequal crossing over A B C D E F G
x
A B C D E F G
A B C D E G A B C D E F F G
Deletion Duplication

27. INSERTION
27

28. Insertion
28

29. Insertion
& Duplication
29

30. INVERSION
30

31. Inversions
• Produced through breakage and
reassociation of chromosome
D
E
C
A B
F G

32. Inversions
• Produced through breakage and
reassociation of chromosome
D
E
C
A B
F G

33. INVERSION
Pericentric Inversion
33

34. Inversion: Pericentric & Paracentric
Pericentric
34

35. Paracentric 35

36. Pericentric Paracentric
Inversion Inversion
INVERSION 36

37. Isochromosome
(Transverse centromeric
division)
37

38. Isochromosome
(Transverse centromeric division)
Example:
•Long arm of X- chromosome remains, short arms lost
•Cytogenetic variant of Turner’s syndrome
38

39. Isochromosome 39

40. TRANSLOCATIONS 40

41. 41

44. Reciprocal Translocation video

45. Robertsonian Translocation
45

47. Acrocentric Chromosomes
(Group D & G)
47

48. Reciprocal (Balanced)
Robertsonian Translocation:
translocation:
Between two acrocentric chromosome
Between any two chromosomes
e.g. Chromosome 13 & 21
Translocation
48

49. Robertsonian Translocation
Common Robertsonian translocations are confined to the
acrocentric chromosomes 13, 14, 15, 21 and 22; short arms of these
chromosomes contain no essential genetic material. 49

50. 50

51. Ring Chromosome
51

52. Ring Chromosome
e.g. r(22): Ring Chromosome no.22
52

55. STRUCTARAL ABERRATION