'Jumping genes' changed uterus to stop laying eggs
Roving pieces of DNA helped early mammals ditch egg-laying in favor of giving birth to live young. These “jumping genes,” or transposable elements, flipped the switch on thousands of genes, turning off ones that build hard eggshells and turning on ones that allow a fetus to develop in the uterus. Researchers report the finding in the Feb. 3 Cell Reports.
“Transposable elements … rewired when and where genes are expressed by giving them new regulatory information,” says study coauthor Vincent Lynch, an evolutionary biologist at the University of Chicago.
In early mammals, traveling DNA moved to new spots in the genome and carried machinery that allowed certain genes to be activated in the presence of a hormone called progesterone, which controls many aspects of pregnancy. These moves flipped on or off genes in the uterus.