J. Clin. Med. 2014, 3(1), 167-175; doi:10.3390/jcm3010167

Maternal Germinal Trisomy 21 in Down Syndrome

Received: 20 December 2013; in revised form: 17 January 2014 / Accepted: 20 January 2014 / Published: 28 January 2014
(This article belongs to the Special Issue Prenatal Genetic Screening and Diagnosis-Part 2)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: It has now been over 50 years since it was discovered that Down syndrome is caused by an extra chromosome 21, i.e., trisomy 21. In the interim, it has become clear that in the majority of cases, the extra chromosome is inherited from the mother, and there is, in this respect, a strong maternal age effect. Numerous investigations have been devoted to clarifying the underlying mechanism, most recently suggesting that this situation is exceedingly complex, involving both biological and environmental factors. On the other hand, it has also been proposed that germinal trisomy 21 mosaicism, arising during the very early stages of maternal oogenesis with accumulation of trisomy 21 germ cells during subsequent development, may be the main predisposing factor. We present data here on the incidence of trisomy 21 mosaicism in a cohort of normal fetal ovarian samples, indicating that an accumulation of trisomy 21 germ cells does indeed take place during fetal oogenesis, i.e., from the first to the second trimester of pregnancy. We presume that this accumulation of trisomy 21 (T21) cells is caused by their delay in maturation and lagging behind the normal cells. We further presume that this trend continues during the third trimester of pregnancy and postnatally, up until ovulation, thereby explaining the maternal age effect in Down syndrome.
Keywords: aneuploidy; Down syndrome; germinal mosaicism; maternal origin; trisomy 21
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MDPI and ACS Style

Hultén, M.A.; Öijerstedt, L.; Iwarsson, E.; Jonasson, J. Maternal Germinal Trisomy 21 in Down Syndrome. J. Clin. Med. 2014, 3, 167-175.

AMA Style

Hultén MA, Öijerstedt L, Iwarsson E, Jonasson J. Maternal Germinal Trisomy 21 in Down Syndrome. Journal of Clinical Medicine. 2014; 3(1):167-175.

Chicago/Turabian Style

Hultén, Maj A.; Öijerstedt, Linn; Iwarsson, Erik; Jonasson, Jon. 2014. "Maternal Germinal Trisomy 21 in Down Syndrome." J. Clin. Med. 3, no. 1: 167-175.

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