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Chromosomal anomalies 2.ppt
- 1. Chromosomal Anomalies (Lecture 2) Dr.Archana Rani Associate Professor Department of Anatomy KGMU UP, Lucknow 30.10.2014
- 2. Trisomy of SexChromosomes • Klinefelter syndrome • Triple X syndrome • Double Ysyndrome
- 3. Klinefelter Syndrome • Chromosomecomplement: 47,XXY • Phenotype: Male • Incidence: 1:1000
- 4. Features of KlinefelterSyndrome • 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
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- 7. Triple X Syndrome(Superfemale) • Chromosome complement: 47,XXX • Phenotype: Female • Incidence: 1:1000
- 8. Features of TripleX 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
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- 11. Double Y Syndrome •Chromosome complement: 47,XYY • Phenotype: Male • Incidence: 1:1000
- 12. Features of DoubleY 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 • Chromosomecomplement: 45,XO • Phenotype: Female • Incidence: 1:5000-8000
- 15. Features of TurnerSyndrome • 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 TurnerSyndrome • Epicanthal folds • Low posterior hair line • Cubitus valgus • Broad chest with widely spaced nipples • Cardiovascular anomalies • Hyperconvex finger nails • Pigmented nevi • Sex chromatin negative
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- 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. Deletion • Loss ofa (generally small) segment of chromosome A B C D E F G A B D E F G C
- 22. Deletion • Arise through spontaneousbreakage – some chromosomes have fragile spots – radiation, UV, chemicals, viruses may increase breakage
- 23. Deletion • May arisethrough unequal crossing over A B C D E F G A B C D E F G x A B C D E F F G A B C D E G Deletion Duplication
- 24. Deletions in Humans •Cri-du-chat 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 – Micro deletion of chromosome 15
- 25. Cri-du-chat syndrome • 1stautosomal 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
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- 27. Prader-Willi and AngelmanSyndromes Prader-Willi Syndrome • Lack of muscle tone in newborn • Poor swallowing reflex • As adult - gross obesity • Mean I.Q. ~ 50 • Microdeletion of 15 Angelman Syndrome • Developmentally delayed • Jerky movements • Stiff, fixed smile • Uncontrolled laughter • Abnormal E.E.G., epilepsy • Microdeletion of 15
- 28. Inversion • 180o reversalof 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
- 29. Inversion • Produced throughbreakage and reassociation of chromosome A B C D E F G
- 30. Inversion • Produced throughbreakage and reassociation of chromosome A B C D E F G
- 31. Types of Inversion ParacentricPericentric
- 32. Translocation • Exchange ofsegments between non- homologous chromosomes F A B C D E L M N O P Q
- 33. Translocation A B C DE F O N M L Q P
- 34. Isochromosome • Centromere ofthe chromosome divides transversely instead of longitudinally • One arm is missing and the other arm duplicated
- 35. Ring Chromosome • Occursdue to loss of both the ends of a chromosome • The broken ends rejoin to form a ring-like chromosome • Rare anomaly
- 36. Robertsonian Changes • Fusion twochromosomes join to form one • Fission one chromosome splits to form two
- 37. REFERENCES 1. Essentials ofAnatomy for Dentistry Students,1st Edition. 2. Langman’s Medical Embryology,11th Edition. 3. Human Embryology, 5th Edition.
- 38. MCQs 1. Klinefelter syndromeis associated with chromosome complement: a) 47,XXX b) 47,XXY c) 47,XYY d) 47,YYY
- 39. MCQs 2. Testicular atrophyis associated with: a) Triple X syndrome b) Double Y syndrome c) Turner syndrome d) Klinefelter syndrome
- 40. MCQs 3. Sex chromatinnegative is a characteristic feature of: a) Triple X syndrome b) Down syndrome c) Turner syndrome d) Klinefelter syndrome
- 41. MCQs 4. All ofthe following are trisomy of sex chromosomes except: a) Turner syndrome b) Klinefelter syndrome c) Triple X syndrome d) Double Y syndrome
- 42. MCQs 5. Partial deletionof 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