Chromosomes don’t look the way you think they are. We now have a 3D image of the real thing

If you’ve ever studied chemistry or biology, there’s a very good chance you’ve come across the common pictorial representation of what a chromosome should look like.

As millions of high school and college students attest, it is a tall, narrow X shape, displaying the appearance of two chromatids joined together after DNA replication, but before cell division is complete, at which point they have separated. to become their own individual chromosomes.

Unfortunately, there is a small problem with this ubiquitous symbol, scientists say, at least in terms of the accuracy of its representation.

“90 percent of the time, chromosomes don’t exist like this,” says physician-scientist Jun-Han Su, formerly of Harvard University.

In a study published this year, Su and her team devised a new way to visualize the 3D organization of chromatin in human cells, giving us a far more meticulous understanding of chromosome chemistry than the iconic X ever can.

(Xiaowei Zhuang Laboratory)

Above: Multicolored chromatin image, using multiplex fluorescence in situ hybridization and super resolution microscopy.

“It is very important to determine the 3D organization,” says senior researcher Xiaowei Zhuang, “to understand the molecular mechanisms underlying the organization and also to understand how this organization regulates the function of the genome.”

Using a new high-resolution 3D imaging system, which involved joining multiple snapshots of genomic loci along DNA strings, the researchers were able to view chromosomes up close in a way never seen before and even glimpse aspects. transcription activity.

High school and CHEM101 will never be the same again. The team is sharing their data online so that other researchers can delve into their analysis and so we can explore this (almost) invisible part of ourselves even more in the future.

“We anticipate broad application of this high-throughput, multiscale, multimodal imaging technology, which provides an integrated view of chromatin organization in its native structural and functional context,” the team explains.

The results are reported in Cell.