Non-Disjunction Disorders

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. Patausyndrome • 47, XX, +13

9. Patau’s Trisomy Syndrome 1 in 14,000 births 47 chromosomesXY or XX 47, +13 #13 Trisomy Nondisjunction

10. Patau’sTrisomy 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 births47 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 chromosomesXY 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. Jacob’s syndrome • XYY • No abnormal appearance/behavior • fertile

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

20. Jacob’s Syndrome Normal physicallyNormal 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’sSyndrome 1 in 1,100 births 47 chromosomesXXY only 47, XXY #23 Trisomy Nondisjunction

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

24. 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 XXXsymptoms • 1/1000 • healthy and fertile - cannot be distinguished from normal female except by karyotype

28. Triple X Syndrome 1 in 2,500 births 47 chromosomesXXX only #23 TrisomyNondisjunction

29. Triple X Syndrome Normally physically Normal mentally Fertile

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