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Nondisjunction disorders

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Presentation on theme: "Nondisjunction disorders"— Presentation transcript:

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

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