Chromosomal Variations - PowerPoint Presentation

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Chromosomal Variations

Dawn Adams

Cytogenetics

CDC’s 2003 Science Ambassador ProgramSlide2

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 SyndromeSlide3

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 Slide4

Types of Polyploidy

Triploidy – three sets of chromosomes

23 x 3 = 69

Tetraploidy – four sets of chromosomes

23 x 4 = 92Slide5

Types of Aneuploidy

Monosomy – one less chromosome

(23 x 2) – 1 = 45

Trisomy – one additional chromosome

(23 x 2) + 1 = 47Slide6

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 SyndromeSlide7

Trisomy 13

Chromosomal Variation – Trisomy 13

(three copies of chromosome 13)

Occurrence – 1 in 5000Slide8

Features of Trisomy 13

Severe developmental delays

Head and facial abnormalities

Extra fingers and toes

Kidney malformations

Heart defects

Early deathSlide9

Trisomy 18

Chromosomal Variation – Trisomy 18 (three copies of chromosome 18)

Occurrence – 1 in 5000Slide10

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 deathSlide11

Down Syndrome

Chromosomal Variation – Trisomy 21 (three copies of chromosome 21)

Occurrence – 1 in 800-1000Slide12

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 deathSlide13

Turner Syndrome

Monosomy of sex chromosome

(only one X chromosome present)

Occurrence – 1 in 2500 live female birthsSlide14

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 problemsSlide15

Klinefelter Syndrome

Trisomy of sex chromosome - XXY

(An additional X chromosome in males)

Occurrence – 1 in 500-1000 malesSlide16

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 problemsSlide17

XYY Syndrome

Trisomy of sex chromosome – XYY

(An additional Y chromosome in males)

Occurrence – 1 in 1000-2000 menSlide18

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 normalSlide19

Conclusions

Variations of chromosomal number involving a set of chromosomes (polyploidy) or an individual chromosome (aneuploidy) can occur

Aneuploidy results in syndromes with distinct characteristicsSlide20

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

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March of Dimes. Chromosomal Abnormalities [online]. 2004. [cited 2004 Feb 6]. Available from URL:

http://www.modimes.org/professionals/681_1209.asp

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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

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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

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March of Dimes. Down Sydrome [online]. 2004. [cited 2004 Feb 6]. Available from URL:

http://www.marchofdimes.com/professionals/ 681_1214.asp

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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

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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

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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

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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

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Hambley, Vaughn. What is XXY? [online]. 2004. [cited 2002 Feb 6]. Available from URL:

http://47xxy.org/XXY.htm

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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

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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

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