Illustration of Jumping genes

1951 Jumping genes

The book of science

Tom Sharp

Barbara McClintock genetics Illustration of Jumping genes

Jumping genes

Something turns genes on and turns them off and, as it turns out, some genes move about. Barbara McClintock discovered the first transposons, responsible for random colorations of kernels of maize, naming them Activator and Dissociator. This disproved the theory that genes were fixed in their positions on their chromosomes, and introduced the uncomfortable fact that Mendelian inheritance and random mutations did not entirely explain genetic variation.


An archaeon, bacterium, or eukaryote does not need all its genes all the time but can express a gene to make a protein as needed. Cells of multicellular organisms differentiate to have different structures and functions even though they contain complete genomes.

Not so simple

“Not so simple, buddy, said the Voice of Reality to the Poet. “Remember all this evolved by chance. Your simple notions, your simple lines don’t begin to describe reality, let alone if you had to make them rhyme!

Barbara McClintock’s papers were highly technical and conceptually difficult. It took thirty years for other scientists to recognize and understand her work. Today, the idea of the regulation of gene expression is a part of introductory genetics.

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