1. Chromosomal Disorders
Bashdar Mahmud Hussen
M.Sc. Biotechnology
Hawler Medical University, Iraq

2. Genetic diseases traditionally - 3 types of diseases
1. genetically determined
2. environmentally determined
about 50% of spontaneous abortuses have chromosomal aberration
hereditary = derived from parents
familial = transmitted in the gametes through generations
congenital = present at birth (not always genetically determined

3. Numerical abnormalities
euploidy - normal 46 (2n)
polyploidy (3n or 4n) - spontaneous abortion
Aneuploidy (whole chr. Missing or extra
trisomy (2n+1) compatible with life
monosomy (2n-1) - autosomal - incompatible with life
- sex chromosomal - compatible with life

4. Numerical Abnormalities
Trisomy 21 (Down syndrome)
Trisomy 18
Trisomy 13
Klinefelter Syndrome
Turner Syndrome
Triple X Syndrome
Most common chromosome abnormalities in aborted fetuses is:
Turner syndrome (45,X)
triploidy
trisomy 16

5. No. of genes on chromosome 21 Mosaic Down syndrome
3. Causes of trisomy
4. Maternal age
Final pair is called the "sex chromosomes."
The sex chromosomes an individual has determines that person's gender; females have two X chromosomes (XX), and males have an X and a Y chromosome (XY).

6. Less frequent disorders
Trisomy 18 (Edwards syndrome) 1:6000
95% (extra number), 5% (translocation)
90% of infants die
Trisomy 13 (Patau syndrome) 1:10000
They have cleft lip and palates, extra fingers and toes, malformed and rotated internal organs

7. Klinefelter Syndrome Found only in males (47, XXY most common)
I in 500 males
Nondisjunction of XX homologues
Sterility
Testicular atrophy
individual is born with three sex chromosome, XXY

8. Turner Syndrome
Found in women with unmistakably female appearance
Absence of ovaries (gonadal dysgenesis)
Usually (45, X) missing one X chromosome
1. X-Chromosome Monosomy 2. X-Chromosome Mosaicism 3. X-Chromosome Defects ( small or large deletion)
individual is born with only one sex chromosome, an X

9. Triple X syndrome 1 in 1,000 girls are born with Triple X syndrome
Menstrual irregularity
Delayed speech & language skill
A mosaic form also occurs where only a percentage of body cell contain XXX
not inherited

11. Prenatal diagnostics amniocentesis - analysis of amniotic fluid
cytogenetic analysis (karyotype)
analysis of various specific genes (PCR)

12. Structural Abnormalities
May involve one or more chromosomes
Usually result from chromosome breakage
The effects of structural changes depend on their size & location
loss of chromosomal material is more dangerous than gain
abnormalities of sex chromosomes are better tolerated than autosomal, abnormalities of sex chromosomes sometimes symptomatic in adult age (e.g. infertility)

13. partial monosomy
proximal deletion (near to centromer)
interstitial deletion
subtelomeric deletion

14. It occurs during meiosis between misaligned homologous chromosomes (unequal crossing-over)
Duplications of oncogenes

15. Non Robertsonian translocation or Robertsonian translocation
A chromosome in which the centromere is located quite near one end of the chromosome. Humans normally have five pairs of acrocentric chromosomes

16. fertility problems.

17. causes Turner syndrome
two identical arms
causes Turner syndrome
causes Turner syndrome

18. Chromosome Mutation Animation