Chromosomal Variations

1. Chromosomal Variations Dawn Adams Cytogenetics CDC’s 2003 Science Ambassador Program

2. Overview I. Chromosomal Variations A. Polyploidy B. Aneuploidy II. Syndromes resulting from Aneuploidy A. Trisomy 13 B. Trisomy 18 C. Down Syndrome D. Turner Syndrome E. Klinefelter Syndrome F. XYY Syndrome

3. Variations in Chromosomal Number • Euploidy – the usual number and sets of chromosomes • Polyploidy – the presence of three or more complete sets of chromosomes • Aneuploidy – the presence of additional chromosomes or missing individual chromosomes

4. Types of Polyploidy • Triploidy – three sets of chromosomes 23 x 3 = 69 • Tetraploidy – four sets of chromosomes 23 x 4 = 92

5. Types of Aneuploidy • Monosomy – one less chromosome (23 x 2) – 1 = 45 • Trisomy – one additional chromosome (23 x 2) + 1 = 47

6. Aneuploidy • When aneuploidy occurs in humans, syndromes can result. Examples include the following: 1. Trisomy 13 2. Trisomy 18 3. Down Syndrome 3. Turner Syndrome 4. Klinefelter Syndrome 5. XYY Syndrome

7. Trisomy 13 • Chromosomal Variation – Trisomy 13 (three copies of chromosome 13) • Occurrence – 1 in 5000

8. Features of Trisomy 13 • Severe developmental delays • Head and facial abnormalities • Extra fingers and toes • Kidney malformations • Heart defects • Early death

9. Trisomy 18 • Chromosomal Variation – Trisomy 18 (three copies of chromosome 18) • Occurrence – 1 in 5000

10. Features of Trisomy 18 • Severe developmental delays • Head and facial malformations • Malformations of the hands and feet • Skeletal malformations • Kidney malformations • Structural heart defects • Early death

11. Down Syndrome • Chromosomal Variation – Trisomy 21 (three copies of chromosome 21) • Occurrence – 1 in 800-1000

12. Features of Down Syndrome • Low muscle tone • Head and facial malformations • Abnormalities of the extremities • Developmental delays • Heart malformations • Increased risk of infectious disease • Early death

13. Turner Syndrome • Monosomy of sex chromosome (only one X chromosome present) • Occurrence – 1 in 2500 live female births

14. Features of Turner Syndrome • Short stature • Lack of ovarian development • Neck abnormalities • Skeletal disorders • Increased risk of osteoporosis, cardiovascular constriction, diabetes, and kidney and thyroid problems

15. Klinefelter Syndrome • Trisomy of sex chromosome - XXY (An additional X chromosome in males) • Occurrence – 1 in 500-1000 males

16. Features of Klinefelter Syndrome • Tall • Sexually underdeveloped • Infertility • Sparse facial and body hair • Developmental delays • Increased risk of autoimmune disorders, breast cancer, osteoporosis, leg ulcers, depression, and dental problems

17. XYY Syndrome • Trisomy of sex chromosome – XYY (An additional Y chromosome in males) • Occurrence – 1 in 1000-2000 men

18. Features of XYY Syndrome • Taller • Comparatively low weight relative to stature • Larger craniofacial dimensions • Severe acne in adolescence • Behavior problems • Learning disabilities • Slightly lower IQ than normal

19. Conclusions • Variations of chromosomal number involving a set of chromosomes (polyploidy) or an individual chromosome (aneuploidy) can occur • Aneuploidy results in syndromes with distinct characteristics

20. References • Fairbanks, D. J. and W. R. Anderson. Genetics: The Continuity of Life. Pacific Grove (CA): Brooks/Cole Publishing Company; 1999. • National Organization for Rare Disorders. Triploid Syndrome [online]. 2004. [cited 2004 Feb 6]. Available at URL: http://www.rarediseases.org/search/rdbdetail_abstract.html? disname=Triploid%20Syndrome. • March of Dimes. Chromosomal Abnormalities [online]. 2004. [cited 2004 Feb 6]. Available from URL: http://www.modimes.org/professionals/681_1209.asp. • National Organization for Rare Disorders. Trisomy 13 [online]. 2004. [cited 2004 Feb 6]. Available at URL: http://www.rarediseases.org/ search/rdbdetail_abstract.html?disname=Trisomy%2013%20Syndrome.

21. References (continued) • National Organization for Rare Disorders. Trisomy 18 [online]. 2004. [cited 2004 Feb 6]. Available at URL: http://www.rarediseases.org/ search/rdbdetail_abstract.html?disname=Trisomy%2018%20Syndrome. • March of Dimes. Down Sydrome [online]. 2004. [cited 2004 Feb 6]. Available from URL: http://www.marchofdimes.com/professionals/ 681_1214.asp. • National Organization for Rare Disorders. Down Syndrome [online]. 2004. [cited 2004 Feb 6]. Available at URL: http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Down%20Syndrome3. • Turner Syndrome Society of the United States. Resources & Research: FAQs [online]. 2003. [cited 2004 Feb 6]. Available from URL: http://www.turner-syndrome-us.org/resource/faq.html.

22. References (continued 2) • National Institutes of Health. Turners Syndrome: Clinical Information [online]. 2004. [cited 2004 Feb 6]. Available from URL: http://turners.nichd.nih.gov/ClinFrintro.html. • American Association for Kilnefelter Syndrome Information and Support. Understanding Klinefelter Syndrome [online]. 2004. [cited 2004 Feb 6]. Available from URL: http://www.aaksis.org/bock.cfm. • Hambley, Vaughn. What is XXY? [online]. 2004. [cited 2002 Feb 6]. Available from URL: http://47xxy.org/XXY.htm. • Texas Department of Health. Birth Defect Risk Factor Series: 47, XYY [online]. 2002. [cited 2004 Feb 6]. Available from URL: http://www.tdh.state.tx.us/tbdmd/risk/risk26-XYY.htm.

23. References (continued 3) • California Center for Health Improvement. XYY Syndrome [online]. 2003. [cited 2004 Feb 6]. Available from URL: http://www.ddhealthinfo.org/ggrc/doc2.asp?ParentID=5199.