Some heirloom varieties of corn contain a cheater chromosome, called
Abnormal chromosome 10 (Ab10). It cheats in the female part of the flower
during meiosis, where it is regularly transmitted about 75 percent of the
time instead of the normal 50 percent.
A team of researchers from multiple universities led by University of
Georgia Professor of Genetics, Kelly Dawe, discovered that Ab10 encodes a
cluster of genes coding for specialized motor proteins. These motor proteins
bind to chromosomes and actively pull them to the reproductive egg cell. The
molecular motors are only found on Ab10, and they enable the Ab10 chromosome
to be transmitted to more than 50 percent of the offspring.
These so-called meiotic drive systems were thought to have evolved and gone
extinct many times. The presence of cheaters has favored the evolution of
new biological rules that thwart the cheaters and ensure overall fairness.
It is rare to visualize a cheater in action, and rarer still to solve its
molecular mechanism. "The mystery had been known for many years before I
began studying it, and we have been trying to solve the problem in our
laboratory for over 20 years," Dawe said. "It was very satisfying to finally
find the genes, and even more satisfying to learn that molecular motors are
powering the process."