Scientists just discovered a new way cells control their genes — it's called 'backtracking'

The human body's roughly 30 trillion cells don't need all of their genes switched on at once. Instead, cells tightly control the activity of their genes — and recently, scientists uncovered a previously unknown way they accomplish that feat.

Human DNA contains approximately 20,000 to 25,000 genes. For a cell to function properly, the genetic code in that DNA is copied down, or transcribed, by an enzyme called RNA polymerase to make a molecule called RNA. Often, the RNA is then translated into proteins, the building blocks of life. There are myriad factors that determine which genes need to be turned on, such as the type of cell and its stage of development.

The recent study, published in February in the journal Molecular Cell, describes a newfound way by which cells control their genes. Called backtracking, it was initially thought to be a response to breaks in the DNA, but it's now being studied for its role in gene regulation.

Discovered in 1997, backtracking is a process in which RNA polymerase, instead of moving forward along the DNA as it reads a gene, shifts back and pauses. This halt then resolves and the enzyme can move ahead again, churning out RNA.

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"In early days, people thought that once RNA polymerase begins transcription, it will finish it without any problems," Evgeny Nudler, a professor of biochemistry at NYU Langone Health, told Live Science. "However, over the years, they realized that the picture is much more complicated." Nudler and colleagues published that first paper about backtracking in 1997.

When RNA polymerase backtracks a short distance, it extrudes a strand of newly formed RNA, causing the transcription process to pause. This extruded RNA is typically chopped off by enzymes, leaving the path clear for RNA polymerase to continue forward again.