1. KARYOTYPING AND NON-DISJUNCTION

2. What is karyotyping? A method of identification of chromosomes Pictures of chromosomes are taken as the cell undergoes mitosis The image is enlarged Individual chromosomes are cut up Chromosomes are matched up based on:  Size (largest to smallest)  Centromere position  G-banding

3. A mess of chromosomes…

4. After karyotyping… a normal male

5. After karyotyping…normal

6. Non-disjunction nondisjunction nondisjunction Non-disjunction is a failure of chromosomes to properly separate during either Stage 1 or Stage 2 of meiosis Upon fertilization the zygote may have one too many chromosomes ( trisomy) or one too few chromosomes (monosomy) All but one monosomy case results in death

7. Non-disjunction Non-disjunction occurs quite often among humans Impact is so severe to the zygote that miscarriage occurs very early in the pregnancy If the baby survives, it develops a set of traits that we call a syndrome

8. Down’s Syndrome Most commonly known trisonomy 1:700 births; 1 in 6 die within 1 st year Average age is 16.2 years Common facial feature Short stature Stubby fingers and toes Large tongue – makes speech difficult

9. Down’s syndrome

10. Down’s Syndrome One of the most common causes of mental disability (IQ is in the 25-75 range) Prone to heart defects, respiratory problems and leukemia

11. Down’s Syndrome Odds of having a Down’s child increases with the age of the mother 1 in 1500 if mom is in early 20’s 1 in 70 if mom is over 35 1 in 25 if mom is over 45

12. Patau Syndrome 1:15,000 births as most fetuses die before term Of those that survive, 5% live to age 3; 45% die within the first month Serious eye, brain, and circulatory defects

13. Patau’s Syndrome

14. Edward’s Syndrome Only 10% survive past one year All die early in infancy Many complications

15. These are the only known trisonomy genetic disorders that result in offspring surviving for a short period of time

16. Non-disjunction of the sex chromosomes These can be fatal Most do survive just fine

17. Klinefelter’s Syndrome Affects 1:500 males XXY Tall, sterile males Normal intelligence Has female characteristics

18. Klinefelter’s Syndrome

19. Jacob’s Syndrome (super male) XYY Somewhat taller than average Slightly below normal intelligence 1:1000 males Extra testosterone

20. XXX (super female?) 1:1000 live births Normal intelligence Fertile No physical problems There are some women who are XXXX and XXXXX – each increasing X results in lesser intelligence and fertility

21. Monosomy – Turner’s Syndrome (XO) 1:2700 births Live normal lives but do not mature sexually at puberty Sterile Short stature Short broad neck Broad chest

22. Other chromosomal issues Deletion – a segment of the chromosome is missing Example: Cri-du-chat (1:1,000,000)  Improperly developed larynx  Severely mentally handicapped

23. Other chromosomal issues Duplication Ex. Fragile X 1:1500 males, 2500 females Most common form of mentally handicapped offspring