1. Chromosomal Anomalies (Lecture 2)
Chromosomal Anomalies (Lecture 2)
Dr. Archana Rani
Associate Professor
Department of Anatomy
KGMU UP, Lucknow

2. Trisomy of Sex Chromosomes
Klinefelter syndrome
Triple X syndrome
Double Ysyndrome

3. Klinefelter Syndrome
Chromosome complement: 47,XXY
Phenotype: Male
Incidence: 1:1000

4. Features of Klinefelter Syndrome
Tall stature; thin build; long lower limbs
Testicular atrophy
Female pattern of pubic hair
High pitched voice
Infertility (aspermatogenesis)
Gynaecomastia
Low level of intelligence
Serum testosterone levels low to normal
FSH and LH levels very high
Sex chromatin positive

5. Klinefelter syndrome: Karyotype

6. Klinefelter Syndrome

7. Triple X Syndrome (Superfemale)
Chromosome complement: 47,XXX
Phenotype: Female
Incidence: 1:1000

8. Features of Triple X Syndrome
Normal in appearance
Difficulty in speech, learning and emotional responses
Mild mental retardation in 15-25% cases
Two sex chromatin Barr bodies
Infertility
Wide-set eyes
Amenorrhoea
Expressionless face
Enamel hypoplasia
Deficient language skills
Delayed development of motor skills

9. Superfemale: Karyotype

10. Superfemale

11. Double Y Syndrome Chromosome complement: 47,XYY Phenotype: Male
Incidence: 1:1000

12. Features of Double Y Syndrome
Normal in appearance
Tall stature
Aggressive behaviour
Problems in motor and language development

13. Monosomies of Chromosomes
Presence of only one member of a chromosome pair in a karyotype
More detrimental than equivalent trisomy
Can involve autosomes or sex chromosomes
Usually abort spontaneously
Monosomy of X chromosome results in XO condition called Turner syndrome

14. Turner Syndrome Chromosome complement: 45,XO Phenotype: Female
Incidence: 1:

15. Features of Turner Syndrome
Short statured female
Sexual infantilism with primary amenorrhoea and sterility
Short, webbed neck
Prominent ears with defective hearing
Small mandible
Defective vision

16. Features of Turner Syndrome
Epicanthal folds
Low posterior hair line
Cubitus valgus
Broad chest with widely spaced nipples
Cardiovascular anomalies
Hyperconvex finger nails
Pigmented nevi
Sex chromatin negative

17. Turner Syndrome: Karyotype

18. Turner Syndrome

19. Structural Chromosomal Abnormalities
Results from chromosome breakage
Followed by reconstitution in an abnormal combination
Breaks in any chromosome may be induced by various factors

20. Structural Chromosomal Abnormalities
Deletion (Deficiency)
Inversion
Translocation
Isochromosome
Ring Chromosome

21. Loss of a (generally small) segment of chromosome
Deletion
Loss of a (generally small) segment of chromosome
A B C D E F G
A B D E F G C

22. Deletion Arise through spontaneous breakage
some chromosomes have fragile spots
radiation, UV, chemicals, viruses may increase breakage

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

24. Large deletions will most probably be lethal
Smaller deletions may allow survival
E. coli: deletions of up to 1% have been observed in living cells
D. melanogaster : deletions of up to 0.1% observed

25. Deletions in Humans Cri-du-chat syndrome Di-George syndrome
Micro deletion of chromosome 5
Di-George syndrome
Micro deletion of chromosome 22
Schizophrenia & Obsessive Compulsive Disorder
Micro deletion of chromosome 22 associated
Angelman syndrome
Micro deletion of chromosome 15
Prader-Willi syndrome

26. Cri-du-chat syndrome 1st autosomal deletion described
Characteristic cat-like cry, which disappears with age
Microcephaly
Severe mental retardation
Congenital heart disease
Hypertelorism (widely separated eyes)
Low birth weight and poor growth
Severe cognitive, speech, and motor delay
Behavioral problems
Excessive drooling

27. Cri-du-chat syndrome

28. Prader-Willi and Angelman Syndromes
Prader-Willi Syndrome
Angelman Syndrome
Lack of muscle tone in newborn
Poor swallowing reflex
As adult - gross obesity
Mean I.Q. ~ 50
Microdeletion of 15
Developmentally delayed
Jerky movements
Stiff, fixed smile
Uncontrolled laughter
Abnormal E.E.G., epilepsy
Microdeletion of 15

29. 180o reversal of chromosome segment
Inversion
180o reversal of chromosome segment
A B C D E F G H I J K
A B C H G F E D I J K
180O

30. Produced through breakage and reassociation of chromosome
Inversion
Produced through breakage and reassociation of chromosome D E C B A F G

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

32. May change phenotype through “position effects”
Inversion
May change phenotype through “position effects”
move active genes to sites generally inactive; lose gene function
move inactive genes to sites generally active; gain gene function
May act to preserve blocks of genes (specific alleles) which function well together

33. Types of Inversion
Paracentric
Pericentric

34. Exchange of segments between non-homologous chromosomes
Translocation
Exchange of segments between non-homologous chromosomes F E L D M N O P C B Q A

35. Translocation
A B C
O N M L
Q P
D E F

36. Isochromosome
Centromere of the chromosome divides transversely instead of longitudinally
One arm is missing and the other arm duplicated

37. Ring Chromosome Occurs due to loss of both the ends of a chromosome
The broken ends rejoin to form a ring-like chromosome
Rare anomaly

38. Robertsonian Changes Fusion two chromosomes join to form one
Fission
one chromosome splits to form two

39. REFERENCES
1. Essentials of Anatomy for Dentistry Students,1st Edition. 2. Langman’s Medical Embryology,11th Edition. 3. Human Embryology, 5th Edition.

40. MCQs
1. Klinefelter syndrome is associated with chromosome complement: a) 47,XXX b) 47,XXY c) 47,XYY d) 47,YYY

41. MCQs 2. Testicular atrophy is associated with: a) Triple X syndrome
b) Double Y syndrome
c) Turner syndrome
d) Klinefelter syndrome

42. MCQs 3. Sex chromatin negative is a characteristic feature of:
a) Triple X syndrome
b) Down syndrome
c) Turner syndrome
d) Klinefelter syndrome

43. MCQs
4. All of the following are trisomy of sex chromosomes except: a) Turner syndrome b) Klinefelter syndrome c) Triple X syndrome d) Double Y syndrome

44. MCQs 5. Partial deletion of short arm of chromosome 5 is a feature of:
a) Angelman syndrome
b) Prader -Willi syndrome
c) Cri-du-chat syndrome
d) All of the above