Chromosome disorders numerical abnormalities http www miscarriage com

Chromosome disorders – numerical abnormalities http: //www. miscarriage. com. au/images/pages/t 21 karyo. jp g

As you probably know. . . 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

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

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

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

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. jp g

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/03 C 0 B 067 CF 5743 D 3 BD 133 1 B 3 D 1 C 79 C 01. jpg

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

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

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

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) http: //www. healthofc hildren. com/images/ gech_0001_0004_0_ img 0280. jpg No certain symptoms – learning problems may result, puberty may be delayed 48, XXXX/49, XXXXX Incomplete puberty, cognitive problems, infertility

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

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?