1. Chromosomes and Karyotypes Chromosomes are comprised of a single, uninterrupted DNA molecule and proteins (histones) A karyotype is a visual display of the chromosomes of an individual.

3. Karyotype A picture of a complete diploid set of chromosomes arranged in pairs of decreasing size

4. Amniocentesis 16-22 Weeks

5. Chronic Villus Sampling (CVS) 10-12 Weeks

6. How Do We Look at the Chromosomes? Cells are treated with Colchicine - WHY? Prevents Spindle Fibers form forming Cells will be stuck in Metaphase Chromosomes will be condensed and VISIBLE Cells are placed in pure water (hypotonic) – WHY?

8. Color or Black and White?

9. Black & White – Most Common Each chromosome has a characteristic banding pattern that helps to identify them; both chromosomes in a pair will have the same banding pattern.

10. Let’s Make It Pretty - Way to Go Photoshop Karyotypes are arranged with the short arm of the chromosome on top, and the long arm on the bottom, called p and q, respectively.

11. Sex Chromosomes- determine an individual’s sex »X and Y chromosome Autosomes-the other 44 chromosomes

13. Normal Female Karyotype

14. Normal Male Karyotype

15. Let’s Make It Pretty - Way to Go Photoshop So, whose Karyotype is this?

16. What is wrong with this picture?

17. Nondisjunction Occurs when homologous chromosomes or sister chromatids fail to separate during meiosis Results in gametes with an abnormal number of chromosomes (missing or extra)

18. Meiosis I Meiosis II Results in Trisomy Results in Monosomy

19. Nondisjunction

20. Does this remind you of something? Hint: What happened when we played – Mutated Tumor suppressor gene?

21. Nondisjunction Consequences Nondisjunction produces abnormal gametes (sperm and egg) Fertilization wit an abnormal gamete can result in Monosomy or Trisomy Monosomy – missing 1 chromosome Trisomy – having 1 extra Most monosomies and trisomies do not survive to birth

22. Down Syndrome Trisomy 21

25. 1 in 700 babies (6000 babies/year) 400,000 Americans Rate increases with maternal age 5% of cases traced to father

27. Turner Syndrome (XO) 1 in 2500 females Monosomy of X chromosome 10% of all miscarriages Highly variable

28. Turner Syndrome (X0)

29. Kleinfelter’s Syndrome (XXY) 1 in 700-1000 males Many times they may not know