1. Nondisjunction Homework for 11/13/14
Fill out notes on the back of page 34, which is the Cell Division Venn Diagram

2. Nondisjunction
Although the events of meiosis usually proceed accurately, sometimes an accident occurs and the chromosomes fail to separate correctly. This is known as nondisjunction.

3. Nondisjunction
The zygote that has been created will have an extra or missing chromosome. This would result in an inherited genetic disorder.
In most cases, the presence of an additional chromosome or missing chromosome results in the death of the zygote.

4. Nondisjunction
Monosomy - the presence of only one chromosome from a pair in a cell's nucleus.
Trisomy – the presence of three chromosomes instead of 2 in a cell’s nucleus.

5. Karyotypes
When you are born, doctors take a sample of your blood and create a karyotype. This will enable the doctor to see if you have any additional or missing chromosomes.
A karyotype is a standardized arrangement of all the chromosomes of a cell.

6. Karyotypes
Homologous chromosomes are paired up, then they are put in order from the LARGEST chromosome pair to the smallest.

7. Karyotypes
2 x chromosomes =
GIRL
autosomes
sex chromosomes

8. Karyotypes Everything okay here?? What gender??
2 different sized sex chromosomes = male

9. Down’s syndrome Everything okay here?? trisomy 21 trisomy 21
decreased muscle tone at birth
asymmetrical or odd-shaped skull
round head with flat area at the back of the head
slanting eyes
small mouth with protruding tongue
single crease on the palm
slowed growth and development
delayed mental and social skills
trisomy 21
trisomy 21

10. Turner’s syndrome Everything okay here?? monosomy X monosomy X
short stature (affects almost all girls with Turner, to different degrees)
failure of ovaries to develop (90-95% of girls)
webbed neck (25%) or short neck (40%)
abnormal fingernails and toenails (70%)
hearing disorders (50-90%)
frequent ear infections in childhood (75%)
monosomy X
monosomy X
monosomy X

11. Turner’s syndrome XO XO XO XO

12. Kleinfelter’s syndrome
Everything okay here??
Kleinfelter’s syndrome
XXY
XXY
XXY

13. Kleinfelter’s syndrome
No symptoms - some men are unaware they have an extra chromosome
Enlarged male breasts - only severe in about 10% of cases
Sparse facial hair
Sparse body hair
Inability to produce sperm
Tallness - more likely to be taller than non-XXY males.
Thinness
Normal intelligence
Language impairment
Delayed language
XXY
XXY

14. Kleinfelter’s syndrome
XXY
XXY
XXY
XXY

15. Patau’s syndrome trisomy 13 trisomy 13 trisomy 13 trisomy 13
Everything okay here??
Patau’s syndrome
trisomy 13
trisomy 13
trisomy 13
trisomy 13

16. Patau’s Syndrome Mental retardation, severe Seizures Small head
Scalp defects (absent skin)
Small eyes (microphthalmia)
Cleft lip and/or palate