Chromosomal anomalies 2.ppt

Biogenetics

1. Chromosomal Anomalies
(Lecture 2)
Dr. Archana Rani
Associate Professor
Department of Anatomy
KGMU UP, Lucknow
30.10.2014

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
•Normalinappearance
•Difficultyinspeech,
learningandemotional
responses
•Mildmentalretardation
in15-25%cases
•Twosexchromatin
Barrbodies
•Infertility
•Wide-seteyes
•Amenorrhoea
•Expressionlessface
•Enamelhypoplasia
•Deficientlanguage
skills
•Delayeddevelopment
ofmotorskills

9. Superfemale: Karyotype

10. Superfemale

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

12. Features of Double Y Syndrome
•Normalinappearance
•Tallstature
•Aggressivebehaviour
•Problemsinmotorandlanguage
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: 1:5000-8000

15. Features of Turner Syndrome
•Shortstaturedfemale
•Sexualinfantilismwith
primaryamenorrhoea
andsterility
•Short,webbedneck
•Prominentearswith
defectivehearing
•Smallmandible
•Defectivevision

16. Features of Turner Syndrome
•Epicanthalfolds
•Lowposteriorhairline
•Cubitusvalgus
•Broadchestwithwidely
spacednipples
•Cardiovascular
anomalies
•Hyperconvex finger
nails
•Pigmentednevi
•Sexchromatinnegative

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. 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. Deletion
•May arise through
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 GA 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
•1
st
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

26. Cri-du-chat syndrome

27. Prader-Willi and Angelman Syndromes
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
•180
o
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
180
O

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

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

31. Types of Inversion
Paracentric Pericentric

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

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

34. Isochromosome
•Centromereofthe
chromosomedivides
transverselyinstead
oflongitudinally
•Onearmismissing
andtheotherarm
duplicated

35. Ring Chromosome
•Occursduetolossof
boththeendsofa
chromosome
•Thebrokenendsrejoin
toformaring-like
chromosome
•Rareanomaly

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

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

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

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

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

41. 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

42. 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