How much of our genome is junk?

One of the oldest and most controversial debates in the field of human genetics revolves around the various answers to the question of, “how much of our genome is functional?” While this could seem like a straightforward question, the answer is anything but simple.


There are fundamental disagreements, even about what the word “functional” should mean. Some define as functional any part of the genome that is transcribed. Others point that some genetic elements harbor potential¬†future function that could be exploited. Still others argue that selfish elements abound that, yes, perform some function, but the function is limited only to their own reproduction, not to the success or reproduction of the host individual. So who is right?

In a recent episode of This World of Humans, I interview Dr. Dan Graur of the University of Houston about his recent paper entitled, An Upper Limit on the Functional Fraction of the Human Genome. For this work, Dr. Graur defines functional as anything in the genome that is maintained by selection. Another way he defines functional is “something that can be destroyed [by mutation].”

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And if you are fascinated by the concept of Junk DNA and want to know more about how it all came about, check out my new book, “Human Errors.” I devote a whole chapter to our sloppy genome!






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