1. Non-Disjunction Disorders

2. What are Non-Disjunction Disorders?!
Non-disjunction is a failure of chromosomes to separate properly (i.e there is an imbalance of genetic information)
Occurs when:
Homologous chromosomes fail to separate properly in Anaphase I
Sister chromatids fail to separate properly during Anaphase II
Having abnormal amounts of karyotypes will overload the cells, which may result in:
The death of the zygote
A person with a non-disjunction disorder being born

3. Key Terms
Karyotypes
The number and visual appearance of the chromosomes in the cell nuclei of an organism or species
Trisomy
A condition in which a diploid organism has one more chromosome than usual. 47
Monosomy
An instance where there is only one chromosome is present, as opposed to the usual two

4. Human male karyotype, written as 46 XY

5. Human female karyotype, written as 46 XX

6. Autosomal Non-Disjunction
Refers to chromosome alterations in autosomes one through twenty-two (1 - 22)
There only 3 trisomies (13, 18, & 21) that result in a baby that can survive for a time after birth
The other trisomies are so devastating that the baby usually dies in utero

7. WARNING!
SOME OF THE PICTURES IN THE FOLLOWING SLIDES MAY BE UPSETTING/TOO GRAPHIC FOR SOME STUDENTS!
IF YOU FEEL THE NEED TO, PLEASE LOOK AWAY FROM THE SCREEN

8. Patau syndrome
47, XX, +13

9. Patau’s Trisomy Syndrome
1 in 14,000 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 a few weeks after birth

11. Edwards Syndrome
47, XY, +18

12. Edward’s Trisomy Syndrome
1 in 4,400 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. Down Syndrome
47, XY, +21

15. Down Syndrome 1 in 1,250 births 47 chromosomes XY or XX
#21 Trisomy Nondisjunction

16. Down Syndrome Short, broad hands Stubby fingers Rough skin
Impotency in males
Mentally retarded
Small round face
Protruding tongue
Short lifespan

17. Non-Disjunction in Sex Chromosomes
Issues arise in homologous pair 23 (X or Y)
Can be fatal
Although many people have these karyotypes and are alive and well.

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

19. Jacob’s Syndrome 1 in 1,800 births 47 chromosomes XYY only 47XYY
#23 Trisomy Nondisjunction

20. Jacob’s Syndrome Normal physically Normal mentally (average IQ)
May have learning disabilities
Increase in testosterone
Perhaps more aggressive
Normal lifespan

21. Klinefelter’s Syndrome
XXY
Found in males

22. Klinefelter’s Syndrome
1 in 1,100 births
47 chromosomes XXY only
47, XXY
#23 Trisomy Nondisjunction

23. Klinefelter’s Syndrome
Scarce beard
Longer fingers and arms
Sterile
Delicate skin
Low mental ability
Normal lifespan
Lower than average testosterone production

24. The only viable monosomy in humans
Turners Syndrome
45, X
The only viable monosomy in humans

25. Turners Syndrome 96-98% do not survive to birth No menstruation
No breast development
No hips
Broad shoulders and neck

26. Trisomy 16, monosomy X
46, X, +16
Not viable beyond 1st trimester

27. Trisomy X 47 XXX symptoms 1/1000
healthy and fertile - cannot be distinguished from normal female except by karyotype

28. Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only
#23 Trisomy Nondisjunction

29. Triple X Syndrome
Normally physically Normal mentally
Fertile

30. 5p- site Cri-du-chat Syndrome Moon-shaped face Heart disease
Mentally retarded
Malformed larynx (have a cat like cry)
Normal lifespan