Scientists Reveal True Picture of DNA: 'X-Shape' Not Real Structure of Chromosome

When you learn about chromosomes, you usually visualize an X-shaped blob of DNA. Yet that isn't the true form of an X chromosome. Now, scientists have created a new method for visualizing chromosomes to paint a truer picture of their shape, revealing a little bit more about this DNA.

"The image of a chromosome, an X-shaped blob of DNA, is familiar to many but this microscopic portrait of a chromosome actually shows a structure that occurs only transiently in cells--at a point when they are just about to divide," said Peter Fraser, one of the researchers, in a news release. "The vast majority of cells in an organism have finished dividing and their chromosomes don't look anything like the X-shape."

In order to better show what chromosomes look like, the researchers decided to put DNA into its proper context in a cell. They developed a new method to visualize a chromosome's shape. More specifically, they created thousands of molecular measurements of chromosomes in single cells, using the latest DNA sequencing technology. By combining these tiny measurements and by using powerful computers, they created a three-dimensional portrait of chromosomes.

"These unique images not only show us the structure of the chromosome, but also the path of the DNA in it, allowing us to map specific genes and other important features," said Fraser. "Using these 3D models, we have begun to unravel the basic principles of chromosome structure and its role in how our genome functions."

The new computer models actually reveal that chromosomes look a bit like a mass of noodles. Don't let that fool you, though. These models put DNA in proper context, showing the complexity of the mammalian genomes in a far more effective way than volumes of text previously had. In doing so, the model reveals the way DNA within chromosomes folds up. In addition, it shows how much genes are expressed, which has direct consequences for health, aging and disease.

"Until now, our understanding of chromosome structure has been limited to rather fuzzy pictures, alongside diagrams of the all too familiar X-shape seen before cell division," said Douglas Kell, BBSRC Chief Executive, in a news release. "These truer pictures help us to understand more about what chromosomes look like in the majority of cells in our bodies. The intricate folds help to unravel how chromosomes interact and how genome functions are controlled."

The findings are published in the journal Nature.