Kaneesha is 26 years old and her husband Marshall is 28. When Kaneesha becomes p
ID: 148498 • Letter: K
Question
Kaneesha is 26 years old and her husband Marshall is 28. When Kaneesha becomes pregnant, she asks her obstetrician about prenatal tests, because a cousin had a child with Down syndrome at age of 27, and her two sisters have each had 2 miscarriages. She tells the doctor of this family history. This is her first pregnancy, although they have been trying for several years The doctor advises Kanesssha to have a maternal serum marker (blood) test, called "triple-test", instead of amniocentesis, because she is under age 35. The triple test is so-called because it measures levels of 3 substances (alpha-fetoprotein, human chorionic gonadotropin, and a form of estrogen). The doctor tells the couple that the test is only a 'screen, and can detect up to 60% of Down syndrome cases that are caused by and extra chromosome 21. Kaneesha gives birth to Nathaniel, who has Down syndrome, but his karyotype does NOT show a trisomy. Kaneesha and Marshall sue the obstetrician, on the grounds that they were advised to take a wrong prenatal test. Why did the doctor advise Kaneesha not to have amniocentesis-and why should she have had the amnio? How can Nathaniel have Down syndrome if his cells have 46 chromosomes? C. What is the risk of Down syndrome in future conceptions for the couple?Explanation / Answer
a) doctor did not advise for amniocentesis because mother age was not above 35, as after this age chances of down syndrome increases. She should have amnio because it was in her family history.
b) this is a translocation type of down syndrome. in this case chromosome pair number 21 is normal but an extra part of chromosome number 21 is attached to chromosome number 14. this is called translocation type of down syndrome.
c) it is hereditary and chances of having of down syndrome is increased.
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