Suppose you were told that most cases of trisomy result from...

Name: Problem 14, Chapter 14: Cell and Molecular Biology: Concepts and Experiments
Uploaded: 2021-11-06T16:45:59-08:00
Duration: 6 min 14 s
Channel: Rabeya Zahid
Description: Suppose you were told that most cases of trisomy result from aging of an egg in the oviduct as it awaits fertilization. What type of evidence could you obtain from examining spontaneously aborted fetuses that would confirm this suggestion? How would this fit with data that has already been collected?

Suppose you were told that most cases of trisomy result from aging of an egg in the oviduct as it awaits fertilization. What type of evidence could you obtain from examining spontaneously aborted fetuses that would confirm this suggestion? How would this fit with data that has already been collected?

Key Concepts

Meiotic Nondisjunction

This concept involves the failure of chromosome pairs to segregate properly during meiosis, resulting in gametes with an abnormal number of chromosomes. In the case of trisomy, fertilization by a gamete that has an extra chromosome leads to a zygote with three copies of a chromosome. This explanation aligns with the observation of trisomies in aborted fetuses and supports the hypothesis if the extra chromosome originates during the egg’s meiotic division.

Maternal Age Effect

This concept refers to the increased risk of chromosomal segregation errors in eggs as a woman ages. Aging eggs may accumulate defects in their meiotic machinery or experience prolonged arrest, which increases the likelihood of nondisjunction events. Evidence showing that most extra chromosomes in trisomic aborted fetuses are of maternal origin would be consistent with this effect.

Cytogenetic and Molecular Analysis of Chromosomes

Analytical techniques such as karyotyping, fluorescent in situ hybridization (FISH), and genotype analysis can identify the origin of extra chromosomes in aborted fetuses. By determining whether the additional chromosome is maternal (often seen as the presence of two distinct maternal alleles) or paternal, researchers can confirm if aging eggs, which are prone to nondisjunction, are indeed responsible for most cases of trisomy. This evidence would integrate with existing data correlating maternal age with increased trisomy incidences.

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