Chromosomal abnormalities are alterations in a person's karyotype that can be detected by studying their chromosomes. There are two main types: numerical abnormalities which involve changes in chromosome number like monosomy, trisomy, Klinefelter syndrome, and Down syndrome; and structural abnormalities which involve changes in chromosome structure like deletions, duplications, translocations, and inversions. Common numerical abnormalities result in conditions such as Turner syndrome, Klinefelter syndrome, and Down syndrome which can cause intellectual disabilities and other health issues.

1. CHROMOSOMAL
ABNORMALITIES

2. What are chromosomal abnormalities?
• These alterations can be detected by studying
the affected person´s karyotype.
• There are many types of chromosomal
abnormalities. However, they can be organized
into two basic groups:
▫ Numerical abnormalities:
▫ Structural abnormalities

3. Normal karyotype
• There are 46 chromosomes (23 homologous ones)
• Homologous chromosomes are evenly banded)

4. Changes in the number of chromosomes of a karyotype.

5. Numerical abnormalities
• Monosomy: an
individual is missing one
of the chromosomes
from a pair.
• Trisomy: an individual
has three chromosomes
instead of a pair

6. Numerical abnormalities. MONOSOMY
• Turner´s syndrome (XO):
▫ Disorder affecting women
▫ An only X chromosome in pair 23 (sex chromosomes)
▫ Clinical symptoms:
 Sterility and underdeveloped genitals
 Short height
▫ Frequency: 1 / 3300 birhts

7. • Turner´s syndrome (XO):

8. Numerical abnormalities. TRISOMY
• Klinefelter´s syndrome (XXY):
▫ Disorder affecting men
▫ Two X chromosomes and one Y chromosome in pair
23 (sex chromosomes)
▫ Clinical symptoms:
 Small genitals and sterility in some cases
 Mild learning disabilities
▫ Frequency: 1.4 / 1000 births

9. • Klinefelter´s syndrome (XXY):

10. Numerical abnormalities. TRISOMY
• Triple X syndrome (XXX) = super female
▫ Disorder affecting women
▫ Three X chromosomes in pair 23 (sex chromosomes)
▫ Clinical symptoms:
 Mild learning disabilities
 Delayed development of speech and motor skills
▫ Frequency: 1 / 1000 births

11. • Triple X syndrome (XXX):

12. Numerical abnormalities. TRISOMY
• XYY syndrome:
▫ Disorder affecting men
▫ One X chromosome and two YY in pair 23 (sex
chromosomes)
▫ Clinical symptoms:
 Skeleton malformations (very tall)
 Moderate learning disabilities and aggressiveness
▫ Frequency: 1 / 2000 births

13. • XYY syndrome:

14. Numerical abnormalities. TRISOMY
• Down´s syndrome:
▫ Disorder affecting women or men (not sex-linked)
▫ Three chromosomes in pair 21
▫ Clinical symptoms:
 Varying degrees of intellectual disability
 Flat head syndrome (brachycephaly)
 Unusually small chin, skin folds at the edge of the eyes,
round face, shorter limbs.
 Various problems with eyesight and heart.
▫ Frequency: 1.5 / 1000 births

15. • Down´s syndrome:

16. Numerical abnormalities. TRISOMY
• Edwards´s syndrome:
▫ Disorder affecting women and men (not sex-linked)
▫ Three chromosomes in pair 18
▫ Clinical symptoms:
 Severe intellectual disability
 Kidney and heart malformations
 Arrested growth and abnormal development of limbs
 Short neck and sternum
▫ Frequency: 1 / 6766 births

17. • Edwards´s syndrome:

18. Numerical abnormalities. TRISOMY
• Patau´s syndrome:
▫ disorder affecting women and men (not sex-linked)
▫ Three X chromosomse in pair 13
▫ Clinical symptoms:
 Intellectual disability
 Heart, genital, finger and brain malformations
 Missing palate
 Deformed feet
▫ Frequency: 1 / 4600 births

19. • Patau´s syndrome:

20. Changes located in the structure of every single chromosome

21. Structural abnormalities
• Deletions: A portion of
the chromosome is
missing or deleted.

22. Structural abnormalities
• Duplications: A
portion of the
chromosome is
duplicated, resulting
in extra genetic
material.

23. Structural abnormalities
• Translocations:
A portion of one
chromosome is
transferred to
another
chromosome.

24. Structural abnormalities
• Inversions: A
portion of the
chromosome has
broken off, turned
upside down, and
reattached. As a
result, the genetic
material is inverted.

25. References
• http://www.genome.gov/11508982#al-5
• http://www.dnaftb.org/#classical
• http://learn.genetics.utah.edu/content/disorders/c
hromosomal/
• Cabrera. A. et al. 2012. 4 ESO. Biology and Geology.
Oxford Education