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Some viruses thwart bacterial defenses with a unique genetic alphabet

DNA has four building blocks: A, C, T and G. But some bacteriophages swap A for Z

viruses from the Siphoviridae (left) and Podoviridae (right) families

Some bacteria-infecting viruses from the Siphoviridae (left) and Podoviridae (right) families illustrated here use a different DNA letter, Z, instead of the standard A.

Science Photo Library/Alamy Stock Photo

By Tina Hesman Saey

- More than 2 years ago

Some bacteria-killing viruses spell out their genetic instructions in a different DNA alphabet.