Scientists Say: Intron

Not all DNA makes proteins

Some parts of DNA code for proteins. Other pieces — called introns — get left out on purpose.

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Intron (noun, “IN-tron”)

This is a section of DNA that is removed during the process of making a protein. DNA contains all of the instructions for life in its code, in stretches called genes. DNA is transcribed into RNA, which is a copy of those instructions. Then the RNA is translated into a protein. But the DNA for a protein isn’t one continuous segment. Often, the parts of the DNA that have protein instructions are peppered with introns. The introns get copied into the RNA but are sliced out before the RNA is translated into a protein.

Though introns may not contain instructions for proteins, they’re not junk. Introns help control how genes are translated into proteins. They can help a single gene code for many different proteins, for example, by determining how the RNA formed from the DNA is spliced together. Introns can also protect important parts of DNA from damage — such as when a strand of DNA breaks.

In a sentence

The wings of peppered moths changed color because an intron jumped from one set of DNA to another — carrying a dark wing color with it.

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Bethany Brookshire was a longtime staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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