1. Nondisjunction disorders

2. Nondisjunction
Nondisjunction—When chromosomes fail to separate during meiosis.
This can happen at anaphase I or II.

3. Human male karyotype, written as 46 XY

4. Human female karyotype, written as 46 XX

5. Down Syndrome
47, XX or XY, +21

6. Down Syndrome 1 in 700 births 47 chromosomes XY or XX
#21 Trisomy Nondisjunction

7. Down Syndrome Short, broad hands Stubby fingers Mentally retarded
Small round face
Protruding tongue
Shorter lifespan
Slanted eyes

8. Patau syndrome
47, XX or XY,
Trisomy 13

9. Patau’s Trisomy Syndrome
1 in 10,000 births
47 chromosomes XY or XX
47, +13
#13 Trisomy Nondisjunction

10. Patau’s Trisomy Syndrome
Small head
Small or missing eyes
Heart defects
Extra fingers
Abnormal genitalia
Mentally retarded
Cleft palate
Most die before birth; some survive a few
weeks after birth

11. Edwards Syndrome
47, XY, +18

12. Edward’s Trisomy Syndrome
1 in 2500 pregnancies, 1 in 6000 births 47 chromosomes
XX=80% XY=20%
#18 Trisomy Nondisjunction

13. Edward’s Trisomy Syndrome
Small head
Mentally retarded
Internal organ abnormalities
90% die before 5 months of age

14. No abnormal appearance/behavior fertile
Jacob’s syndrome
XYY
No abnormal appearance/behavior
fertile

15. Jacob’s Syndrome 1 in 1,000 boys 47 chromosomes XYY only
#23 Trisomy Nondisjunction

16. Jacob’s Syndrome Normal physically Normal mentally
Associated with risk of learning disabilities.
Once thought to be more aggressive
Normal lifespan

17. Klinefelter’s Syndrome
XXY, male

18. Klinefelter’s Syndrome
1 in births
47 chromosomes XXY only
#23 Trisomy Nondisjunction

19. Klinefelter’s Syndrome
Scarce beard
Longer fingers and arms
Sterile
Low testosterone
Delicate skin
Possible learning disabilities
Normal lifespan
More X chromosomes could cause worse symptoms (XXXY)

20. Turner Syndrome
45, X

21. Turner Syndrome Occurs in about 1 in 2,500 births
Many do not survive to birth
No menstruation
No breast development
No hips
Broad shoulders and neck

22. Trisomy X
47 XXX symptoms
healthy and fertile - cannot be distinguished from normal female except by karyotype

23. Triple X Syndrome 1 in 1,000 births 47 chromosomes XXX only
#23 Trisomy Nondisjunction