Chromosome disorders – numerical abnormalities

1. Chromosome disorders – numerical abnormalities http://www.miscarriage.com.au/images/pages/t21karyo.jpg

2. A human normally has 46 chromosomes in each and every cell Every chromosome comes as a double, we inherit one from each of our parents Sex chromosomes are the exception Sex is determined by the presence or absence of the Y chromosome Female 46,XX – Male 46,XY As you probably know...

3. Chromosome abnormalities • Polyploidy • Aneuploidy • Structural abnormalities • Usually abnormal chromosomes cause miscarriage • In Finland these problems affect 6 children per thousand newborns • Our subject today is aneuploidy in humans and the diseases caused by it

4. Aneuploidy • Individual whole chromosomes are missing or extra • In autosomal as well as sex chromosomes • Trisomy: one whole extra chromosome present • In humans only viable trisomies: 21, 13 and 18 • Multiple sex chromosomes • Monosomy: one whole chromosome missing • In humans the only viable monosomy is 45,X

5. Aneuploidy • Numerical chromosome anomalies often arise in meiosis, the process of producing germ cells • Other reasons: fertilization ”gone wrong”, later mutations

6. Trisomy 21 • The most common trisomy • Incidence 1:600 in Finland • Also known as Down syndrome • In 80 % of the cases the extra chromosome comes from the mother • AGE http://www.dsala.org/graphics/photos/baby_angel.jpg

7. Symptoms • Heart problems • Intestinal problems • Prone to infections • Typical facial features • Lower IQ • Down men cannot reproduce • Only half survive to the age of 40 http://test.cvtcollege.org/Ac_Programs/dms_vascular/images/03C0B067CF5743D3BD1331B3D1C79C01.jpg

8. Trisomy 13 • Symptoms • Cleft lip/palate • Brain malformation • Heart problems • Polydactyly: extra fingers and toes • Patau syndrome • Incidence 1:5000 • If the fetus survives, the developmental problems are severe, lifespan 1-2 months at most http://www.yorku.ca/earmstro/journey/images/pals.jpeg

9. Symptoms Heart problems Internal organ deformaties Mental retardation Difficulties eating and breathing Small head, back of the head very prominent Typical facial features Trisomy 18 • Edward's syndrome • Incidence 1:3000 • Average lifespan 1-2 months, seldom over a year (5-10 %)‏

10. Abnormalities in the number of sex chromosomes • In males • 47,XXY Klinefelter syndrome (1:600 baby boys)‏ • No deformities, but testicles don't develop normally, which affects development in puberty • Infertility • 47,XYY, extra Y chromosome (1:1 000 baby boys)‏ • Prolonges growth, some have learning difficulties or emotional problems • 48,XXXY/48,XXYY/49,XXXXXY • Developmental disabilities, genital deformity

11. Abnormalities in the number of sex chromosomes • In females • 45,X Turner syndrome (1:5 000 baby girls)‏ • Short stature, low hairline, cognitive problems, no puberty, infertility, heart problems • 47,XXX extra X chromosome (1:600 baby girls)‏ • No certain symptoms – learning problems may result, puberty may be delayed • 48,XXXX/49,XXXXX • Incomplete puberty, cognitive problems, infertility http://www.healthofchildren.com/images/gech_0001_0004_0_img0280.jpg

12. Summary • Aneuploidy means having too many or too few chromosomes • Usually pregnancies with aneuploidic fetuses don't come to term • Triploidies 13 and 18 cause severe problems and early death • Triploidy 21 is a milder condition in comparison • Changes in sex chromosome number often cause so little problems that they are left undetected

13. Class activation • Should these children be given a chance to live? • What would you do if you found out that your unborn child had one of these conditions? • Severe vs less severe • Would you even want to test your child for these conditions?