2. Chromosomal aberrations
Definition :-
“Any deviation either in number or structure of the
chromosomes is referred as chromosomal aberrations”
Types :-
1) Structural aberrations.
2) Numerical aberrations.

3. Structural aberrations
 Stable:–
- Deletions
- Translocation
- Insertion
- Inversions
- Isochromosomes
 Unstable:-
- Dicentric
- Ring chromosomes

4. Numerical aberrations
 Autosomal :-
 Monosomies are fetal – Abortion.
 Trisomies are common.
Trisomy 21 / Down’s syndrome
Trisomy 18 / Edwards syndrome
Trisomy 13 / Patau syndrome
 Sex chromosome related :-
Turners syndrome / 45X
Polysomy X syndrome / e.g. XXX, XXXX
Klinfelters syndrome / 47 XXY

5. Turners syndrome
Introduction:
 Monosomy X
 Described by Turner in 1938
 Cytogenetics – ford et al. 1959
 Affects females only, 1:2500
 “XO” instead of “XX”
Clinical features:
 Phenotype – Female
 short stature (approx.
4’8”), short neck with webbed
appearance
 Cubitus valgus

6.  low hairline at the back of
the neck, low set ears
 Broad chest, widely spaced
nipples
 High arched palate
 Lymphoedema over feet
 CVS: coarctation of aorta
VSD

7.  Urinary: Horseshoe kidney
Renal hypoplasia or aplasia.
Duplication of ureter

8.  Shorter than average/slow growth rate
 No growth spurts during puberty
 Non-functioning ovaries
 No production of estrogen or progesterone
 Infertility
 Middle Ear infections leading to eventual loss of
hearing
 Problems with math, memory skills, and fine-finger
movements
 Discolored spots on skin

9.  Broad chest/widely spaced nipples
 Heart murmur due to narrowing of aorta
 High blood pressure
 Minor vision issues
 Scoliosis
 Osteoporosis (thinning of bones) due to lack of
estrogen

10.  Obese weight (due to an underactive thyroid)
 Drooping eyelids
 Problems with breast development
 Short fingers and toes
 Extra skin on the neck (webbed neck)
 Swelling of the hands and feet
 Soft nails that turn upward at the ends
 Irregular rotation of wrist and elbow joints

11.  Loss of ovarian functions (infertility)
 Heart defects
 Kidney problems
 Visual impairments
 Ear infections and hearing loss
 High blood pressure
 Weak bones

12.  Range of intellectual development usually normal
 However, they seem to have difficulty with specific
skills
 Learning disabilities
 Especially in math
 Behavioral problems
 Problems with concentrating and remembering

13. Cytogenetics
60% - typical 45XO
40% are due to Structural or moasic
 Usually caused by non-disjunction
 Pair of sex chromosomes does not separate during
formation of either egg or sperm
 When abnormal egg unites with normal sperm to form
embryo…
 May end up missing that sex chromosome
 Be X instead of XX

14. Investigations:
1. Barr Body
Examination
2. Dermatoglyphics
high total ridge count
Distal axial triradius
3. Karyotyping

15. Management
 Counseling of parents and patient
 Noramal or slightly less normal intelligance
 Anabolic steroids at 10-12 yrs of age helps to gain
weight.
 Oestrogen administration for secondary sexual
character.

16. Is Turner Syndrome “hereditary”?
Although it is a genetic
disorder, it is not
usually hereditary
There are no known
environmental causes
of the syndrome
Women with Turner
Syndrome are usually
infertile

17. Polysomy X
Polysomy X/ XXX syndrome/ Super female
 affects females only, often asymptomatic
 “XXX” instead of “XX”
 Characteristics:
 small head, tall stature
 menstrual irregularities, delayed puberty, premature
menopause, infertility

18. Klinefelter’s Syndrome
introduction
 Described by- Harry Klinefelter 1942
 Karyotype- Jacob & Strong 1959
 47,XXY
 Male phenotype with sex chromatin positive

19. Clinical features
 Tall, thin, Eunuchoid.
 Long legs
 Poorly developed secondary sexual
characters
 Testis are smaller
 Scrotum & penis- Hypoplasia
 Pubic, chin, chest & axillary hairs:
Absent / poorly developed
 Normal intelligence, verbal IQ low

20.  Gynaecomastia
 Testicular biopsy: Hyalinization of seminiferous tubules
 No spermatogenesis
 Sterile
 Chromatin positive cells
 Low serum testosterone
 High FSH & LH levels

21. Cytogenetics
 Most cases- 47, XXY
 15% cases: mosaic (46,XY / 47, XXY)
- Testicular development & mental status may be normal
 60% cases: Maternal X
- Meiotic or postzygotic nondisjunction
- 47, XmXmY
 40% cases: Paternal X
- Nondisjunction during first meiotic division of
spermatogenesis
- 47, XmXpY

23. Some variants
48, XXXY
48,XXYY
49, XXXXY
 Addition of extra X causes
-severe dysmorphism
-mental retardation

24. Investigation
 Cytogenetic studies:
Prenatally of fetus for screening
Postnatally: prompted by clinical signs:
Infants:- hypospadias, cryptorchidism, microphallus,
developmental delay
Kindergarten/elementary school - language delay,
learning disability/behavioral problems
Older boys/adolescent males- eunuchoid body habitus,
gynecomastia or small testes
 Hormone testing
Age 12-14: plasma FSH, LH, estradiol and
testosterone, with minimal response to hcg stim

25. XYY syndrome
 affects males only, 1:1000
 Characteristics:
 tall, about 3 inches taller than normal on average
 severe acne
 normal fertility, normal sexual drive
 Increased aggressiveness
 Associated with antisocial behaviour

26. Sex Developmental errors with
normal chromosomes
 Ambiguous genitalia- difficult to assign sex.
 Only testes, only ovaries, both tesis &Ovaries on
alternate side
 Normal sex chromosomes: single gene defect
 Karyotyping is imp. For Diagnosis & councelling.

27. Hermaphroditism
a hermaphrodite is an organism
that has reproductive organs normally
associated with both male and female
sexes.
Types
 True Hermaphroditism
 Pseuo Hermaphroditism
- Male Pseuo-hermaphroditism
- Female Pseuo-hermaphroditism Hermaphroditus, the son of
the Greek god Hermes and
the goddess Aphrodite,
origin of the word
"hermaphrodite".

28. True hermaphroditism
an intersex condition in which an individual is born
with ovarian and testicular tissue.
 Ovary underneath each testicle on the other
 Ovotestis
 External genitalia are often ambiguous, the degree
depending mainly on the amount of testosterone produced
by the testicular tissue between 8 and 16 weeks of
gestation.

29. Causes
 It can be caused by the division of one
ovum, followed by fertilization of each haploid
ovum and fusion of the two zygotes early in
development.
 an ovum can be fertilized by two sperm followed
by trisomic rescue in one or more daughter cells.
 Two ova fertilized by two sperm will occasionally
fuse to form a tetragametic chimera.
 If one male zygote and one female zygote fuse, a
hermaphroditic individual may result.
 It can be associated with mutation in the SRY
gene.

30. Pseudohermaphroditism
 is the condition in which an organism is born with
secondary sex characteristics or a phenotype that is
different from what would be expected on the basis of
the gonadal tissue (ovary or testis).
 if ovaries, then male external sexual anatomy
 if testes, then female external sexual anatomy