In humans, a fertilized egg is no guarantee of reproductive success. Most embryos stop developing and perish within days of fertilization, usually because they have an abnormal number of chromosomes. Now, researchers at Columbia University Vagelos College of Physicians and Surgeons have found that most of these mistakes are due to spontaneous errors in DNA replication in the earliest phase of cell division.
The findings provide new insights into the basic biology of human reproduction and in the long term could lead to improvements in the success rate of in vitro fertilization (IVF). The study was published online July 19 in the journal Cell.
Challenging task for early embryos
Approximately 24 hours after a human egg is fertilized, the process of cell division begins. During cell division, the entire genome — 46 chromosomes containing more than 3 billion base pairs of DNA — must be faithfully duplicated. The duplicate sets of chromosomes must then be separated so that each daughter cell receives a complete set.
In many human embryos created for IVF, something goes wrong and some cells within the embryo have too few or too many chromosomes.
“Duplicating the genome is a challenging task for the early embryo,” says study leader Dieter Egli, PhD, the Maimonides Assistant Professor of Developmental Cell Biology (in pediatrics) at Columbia University Vagelos College of Physicians and Surgeons.
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