01. Why are Hybrids Sterile?
Daniel Barbash
Daniel A. Barbash, Molecular Biology and Genetics, identified two genes from two fruit fly species that interfere with each other and prevent the production of male offspring. This is the first example of two genes interacting to cause sterility or lethality in a species hybrid. The discovery supports the Dobzhanzy-Muller theory of the 1930s, holding that hybrid incompatibilities are caused by genes that evolved from a common ancestor, but as the genes evolved in distinct species, they began to code for proteins that no longer work in the other species. Barbash’s lab studied a rarely occurring mutation in a Drosophila melanogaster gene called Hmr (Hybrid male rescue) and a similar mutation in a D. simulans gene called Lhr (Lethal hybrid rescue) that make these genes nonfunctional. The discovery may lead to determining whether hybrids die because of additional genes like Hmr and Lhr or because of subtle differences between the chromosomes of the two species. Barbash’s research will help scientists understand what causes lethality or sterility in hybrids and how species evolve from a common ancestor.