1. 4.4 Abnormal Meiosis: Nondisjunction
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2. Problem
Problems with meiosis may lead to genetic disorders or infertility.

3. Contributing Factors
Disease
Environmental factors
Random errors

4. Non-disjunction
Homologous chromosomes fail to separate during meiosis.

5. One daughter cell has one extra chromosome
One daughter cell has one extra chromosome. One daughter cell has one missing chromosome

6. Too much or too little protein is made.

7. trisomy
3 copies of a chromosome Examples: trisomy 21-Down’s syndrome trisomy 13-Patau’s syndrome

8. monosomy
1 copy of a chromosome
Example: 0X -Turner’s syndrome

9. Risk Factors Increase with Age
The risk of non-disjunction increases with age. 1 in 800 children is born with Down Syndrome.

10. A woman in her 20’s has a 1 in 1000 chance of delivering a child with Down Syndrome.

11. A woman in her 40’s has a 1 in 40 chance of delivering a child with Down Syndrome

12. Karyotype
Prepared using white blood cells frozen in metaphase, photographed and sorted

13. Prenatal Testing
After age 35. At 8 weeks, the chorionic villus sampling (CVS) can remove cells from the outer membrane surrounding the embryo Later, amniocentesis can be done Between weeks a multiple markerblood test can be done.

14. Infertility
10% of couples in Ontario are unable to produce children -poor sperm or egg quality -blockages in the fallopian tube or vas deferens

15. Assisted Reproductive Technology
-increased gamete production -fertility drugs -in vitro fertilization

16. In Vitro Fertilization
Use hormone therapy to stimulate egg production
Harvest eggs
Fertilized with sperm in a petri dish
Embryos are transferred to the womb

17. Intracytoplasmic sperm injection
ICSI One sperm is inserted into the egg

18. Laser-assisted Hatching
Using a laser, a whole is made in the zona pellucida, the outer shell of a fertilized egg, allowing the embryo to hatch and implant in the uterus.

19. Artificial Insemination
Semen is placed into the reproductive tract of a female. -breeding of prized animals (race horses, dairy cows) -efforts to save endangered species

20. Advantages of AI Less costly than transporting animals
Animals that will not breed in captivity can still reproduce
Sperm can be frozen for a long time
Banks of sperm can be maintained
Disadvantage: Belief that it is more important for animals to breed in the wild.