What properties are observed in DNA replication

Observe DNA replication with the microscope

06.05.2016



The genetic material must be copied before each cell division. Scientists working with biology professor M. Cristina Cardoso have now followed the starting points of DNA duplication in cells of humans and mice under the microscope for the first time. Together with researchers led by physics professor Barbara Drossel, they developed a computer model that describes the spatial and temporal distribution of the replication sites.

In humans and other higher living beings, the genetic material is well packed with proteins in the cell nucleus. Before cell division, the cell has to start up a complex unpacking and copying machinery so that the daughter cells receive the same genetic makeup as their predecessor. Billions of base pairs of DNA then have to be doubled - and as precisely as possible, because copying errors can lead to cancer and other diseases. For several decades, researchers have suspected that the cell starts replicating the genetic material at thousands of locations on the DNA at the same time. Otherwise the process would take way too long.

"With new methods of super-resolution microscopy, we have succeeded for the first time in visualizing and quantifying the many replication sites in the cell nucleus," reports M. Cristina Cardoso, Professor of Cell Biology and Epigenetics at TU Darmstadt. Together with colleagues from Munich and Berlin as well as from Russia, England and France, Cardoso succeeded in gaining a fascinating look into the cell nucleus, which shows the replication sites in color and in 3D. The scientists looked at both human cells and mouse cells over a complete cell cycle. To do this, they combined super-resolution microscopy with computer-controlled image analysis.

In addition, Cardoso's group, together with researchers headed by TU physics professor Barbara Drossel, is presenting a computer model that describes the spatial and temporal distribution of the replication sites in the cell nucleus and corresponds well with microscopic observation. According to the model, the starting points of replication are initially randomly scattered across the genetic material. The DNA duplication then spreads according to the domino principle: New replication sites are created in the vicinity of DNA sites that have already been copied. Cardoso postulated this domino effect over ten years ago. Now, at last, their assumption has been confirmed and a fundamental question of DNA replication has been clarified.

»Original publication 1

»Original publication 2

Source: Technical University of Darmstadt


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