When does maternal age-dependent trisomy 21 arise relative to meiosis?

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · American Journal of Human Genetics

OSTI ID:443757

Zheng, Chang-Jiang ^[1]; Byers, B ^[2]

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1. National Inst. of Deafness and Other Communication Disorders, Bethesda, MD (United States)
2. Univ. of Washington, Seattle, WA (United States)

Polymorphic DNA markers have recently been used to estimate the fraction of trisomy 21 (Down syndrome) cases that may be attributable to postzygotic nondisjunction - indicative of a loss in the fidelity of the first few cell divisions after fertilization. In these studies, a postzygotic nondisjunction is defined as a case in which two chromosomes of the trisomic set are homozygous for all informative markers (i.e., for those markers that were heterozygous in their parent of origin). These studies estimate that the postzygotic mutation mechanism accounts for 4.5% (11/238) and 3.5% (9/255) of their cases, respectively, but their estimates may actually be conservative, since all noninformative haplotypes (frequency not reported) are arbitrarily attributed to meiosis II-type nondisjunction. Nevertheless, even the conservative estimates would, if confirmed, constitute a new and nonnegligible source of chromosomal segregation errors leading to trisomy. These studies` conclusions are supported by the observation that the 20 reported {open_quotes}postzygotic{close_quotes} cases (5 paternal and 15 maternal) appear to be less dependent on maternal age (mean maternal age 28.4 years) than maternal meiosis I-type failures (mean maternal age 31.2 years). However, given the limited sample size involved, one should be cautious in positing the absence of a maternal age effect. 5 refs., 1 fig.

• OSTI ID: 443757
• Journal Information: American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: 1 Vol. 59; ISSN AJHGAG; ISSN 0002-9297
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
AGE DEPENDENCE
BIOLOGICAL MARKERS
GENETICS
HEREDITARY DISEASES
HUMAN CHROMOSOME 21
MEIOSIS
NON-DISJUNCTION
PATIENTS
ZYGOTES