2. TABLE OF CONTENT, 4D
1. Definition
2. Detection
3. Different types
4. Different human condition due to
chromosomal abnormalities
3. chromosomalabnormalities ?????
• A chromosomal abnormality, anomaly,
aberration or mutation is a missing, extra, or
irregular portion of chromosomal DNA.
• Chromosomal abnormality can form an atypical
number of chromosome or a structural
abnormality in one or more chromosomes.
4. Detection of chromosomal abnormalities
It can be detected by studying and comparing
the affected person’s karyotype(number and
appearance of chromosomes).
Some of the techniques of chromosomal
abnormalities detection are amniocentesis, bone
marrow sampling for screening leukemia,
chorionic villus sampling etc.
5.
6. How do chromosomal abnormalities happens
???
Usually due to error in cell division i.e.
mitosis and meiosis
Different types of chromosomal abnormalities
can be organized into two basic groups,
1] Numerical abnormalities
2] Structural abnormalities
7. Numerical abnormality
Also called aneuploidy
Abnormal number of chromosome
Either chromosome is missing from the pair
or presence of more then two chromosome
8. Aneuploidy could be,
MONOSOMY
Missing one of the
chromosomes
from a pair
TETRASOMY
Four
chromosome
instead of a pair
TRISOMY
Three
chromosomes
instead of a pair
More than
four some
time, but
rare
9. MONOSOMY
Form of aneuploidy with the presence of
only one chromosome from a pair.
Human condition due to monosomy;
1] Turner’s syndrome
2] Cri du chat syndrome
3] 1p36 deletion syndrome
10. Numerical abnormalities, monosomy
Turner’s syndrome (XO)
Also known as 45,X or 45,XO
Disorder affecting women
Only X chromosome present in pair 23(sex
chromosomes)
Frequency : 1/3300 births
No cure for turner’s syndrome is known,
treatment is available.
11. Numerical abnormalities, monosomy
Cri du chat
Also called as Chromosome 5p deletion
syndrome or 5p monosomy or partial
monosomy
Rare chromosomal abnormality with the
frequency of 1/50,000 live birth
More common in female
12. Numerical abnormalities, monosomy
1p36 deletion syndrome
Congenital genetic disorder
Occurs due to the deletion of outermost light
band of the short arm of chromosome 1
Frequency : 1/5,000-10,000 birth
Symptoms could be intellectual disability,
delayed growth, distinct facial features etc
13. TRISOMY
Form of aneuploidy with the presence of three
chromosome instead of normal single pair
chromosome
Human condition due to trisomy
1] Down syndrome
2] Klinefelter’s syndrome
3] Edward syndrome
4] Patau’s syndrome etc.
5] Triple X syndrome
Down
syndrome
14. Numerical abnormalities, trisomy
DOWN SYNDROME
Also known as trisomy 21
Known by karyotype 47,XX,+21 for female
and 47,XY,+21 for males
Three chromosome in pair 21
Disorder affecting both male and female
(not sex-linked)
Frequency : 1.5/ 1000 birth
16. Numerical abnormalities, trisomy
EDWARD SYNDROME
Also called trisomy 18
Represented as 47,XX,+18 for female
Caused by the presence of all or part of
a third copy of chromosome 18
Disorder affecting both male and female
Frequency: 1/7000 birth
17. Numerical abnormalities, trisomy
PATAU SYNDROME
Also called as trisomy 13
Represented as 47,XX,+13 for female
Disorder Not sex linked
Three X chromosome in pair 13
Frequency : 1/4000 births
18. Numerical abnormalities, trisomy
TRIPLE X SYNDROME
Disorder affecting women
Three X chromosomes in pair 23, also
called super female
Represented as 47,XXX
Frequency : 1/1000 births
19. TETRASOMY
Form of aneuploidy with the presence of
four chromosome instead of normal single
pair chromosome
Human condition due to trisomy
1] cat eye syndrome, tetrasomy 22
2] pallister-killian syndrome, tetrasomy 12p
3] 48,XXXX syndrome/tetrasomy X etc.
20. Cat eye syndrome, tetrasomy 22
Rare disorder associated with the presence of an
extra chromosome fragment of short arm (p) and a
small portion of long arm (q) of chromosome 22
,resulting in total of four copies instead of normal
two copies in a cell.
Some CES patient may have vertical colobomas,
thus name coined as cat eye syndrome
23. TETRASOMY X / 48,xxxx
Occurs in female only
Presence of four X chromosome instead
of two
When homologous X chromosome fails
to separate in the formation of the egg
or sperm, tetrasomy X may arise.
24. STRUCTURAL
ABNORMALITIES
It occur when there is change in the
structure or components of the chromosome
The change may be when,
Part of chromosome is missing
Part of chromosome is extra
Part of chromosome has switched places
with another part
25. Several forms of structural
abnormalities
1. Deletion
2. Duplication
3. Insertion
4. Inversion
5. Translocation
6. Ring chromosome
7. Isochromosome
26. Structural abnormalities
DELETION
• Loss of a portion of chromosome or
a sequence of DNA during
replication
• Deletion of nucleotide can cause
frame-shift mutation
• Deletion could be,
a) Terminal deletion
b) Intercalary deletion
c) micro deletion
27. Structural abnormalities
DUPLICATION
Portion of chromosome is duplicated, resulting in
extra genetic material.
A chromosomal duplication is usually caused by
abnormal events during recombination
Charcot Marie Tooth diseases type 1A :- human
disorders due to duplication of peripheral myelin
protein 22 (PMP22)
29. structural abnormalities
INSERTION
A portion of one
chromosome has
been deleted from
its original place
and inserted into
another
chromosome
Can often occur in
microsatellite
regions due to the
DNA polymerase
slippage
