DOWN’S SYNDROME By: Madison Pierce

WHAT CAUSES IT?  Excessive amounts of Chromosome 21  Most common cause is non-disjunction: Affected individual contains an entire extra chromosome in all their cells because meiosis doesn’t occur properly. No known cause.  Mosaicism & Translocation are also causes, but are more rare.  Mosaicism: some cell lines have an extra chromosome, some don’t, usually 46 chromosomes.  Translocation: when part of or a whole chromosome breaks apart and attaches to a different one, usually 14.

HOW IS IT DIAGNOSED?  Can be diagnosed through either pre-natal screening or after delivery.  Pre-Natal Screening: Can be performed after the 15 th week of pregnancy, blood is drawn and three different chemical levels are observed (triple screen test). These readings, along with the age of the mother, can be combined to estimate the risk of Down’s.  Amniocentesis: Amniotic fluid is extracted from the womb and a karyotype can be made from it.  After Delivery Symptoms: upward slanting eyes, decreased muscle tone, small mouth, abnormal ear shapes, flattened nose.

CAN IT BE INHERITED?  Translocation can cause Down’s to be passed through generations  Is a recessive trait, so the mother can carry it. There is around a 12% chance that an affected mother will have an affected baby.  Men with Down’s are sterile and cannot reproduce.

SUGGESTIONS  Since Judy is pregnant and over 40, she is at high risk for a number of things to happen to her baby, whether it be a genetic disorder like Down’s or losing the baby all together.  It would be wise to have genetic screening performed to learn whether or not the child may be at risk for genetic disorders.  The doctor wouldn’t have to specify the gender of the child or anything like that, just if the child had the potential to be genetically altered.

CITATIONS  Down's Syndrome. (2002). Retrieved from Your Genes, Your Health website: