Blog 10.2 Mitotic Chromosome 3-Dimensional Structure Mapping

5-year-old's rendition of the human chromosome

Well I couldn't wait to write about this one, so I am doing another blog for this week! Finally, after approximately one and a half centuries of debate, the scientists at MIT pinpointed a universal method in all types of cells of condensed mitotic chromosome organization. Before this, scientists had no way of knowing the exact method of how DNA was condensed in the chromosome, as microscopes were not technically advanced enough to observe the process, which led to different suggested methods. It was already known that DNA had to be tightly condensed in order for successful transportation to daughter cells, but how it actually folded was debatable. The most common textbook explanation of how DNA was condensed was via multifold coiling, where coils form coils form coils (supercoils). However, there was another explanation of how DNA was condensed, stating that a series of loops were formed, attaching to a linear axial structure, ultimately becoming the chromosomal backbone. To solve this dilemma, scientists used chromosomal conformation capture to find exact contact points on different chromosomes during the metaphase part of mitosis, creating 3D models from contact point spatial arrangement. After comparing this model to the two previously suggested models, we can now throw the multifold coiling method out the window. In actuality, the chromosome was compacted in two phases: first to form loops with a circumference of approximately 100,000 base pairs, and second to tightly compress these loops like a slinky. What's strange about this is that condensed DNA is not as highly organized as we had originally thought it to be. Loops formed pretty much randomly, meaning that condensing is variable. My question to you is this: What things can scientists experiment on once the entire mitotic chromosome or
ganization process is understood?

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