Box 4 | The dominant female sterile technique for selecting homozygous germ-line clones 

Dominant female sterile (DFS) mutations in the ovo gene (ovo^D mutants) cause female germ cells to die during early oogenesis, and therefore completely block egg production. These mutants can be used to eliminate non-recombinant cells in Flp/FRT screens for mutations that give phenotypes in germ-line clones, by placing them on the FRT chromosome arm that is to be selected against. In the absence of recombination, the ovo^D transgene kills all of the germ cells, so the only egg chambers to survive are those that have lost ovo^D and are homozygous for the other FRT chromosome arm (see figure). By mutagenizing this chromosome, genetic screens can be carried out for lethal mutations that give maternal-effect phenotypes, in which 100% of the eggs that are laid derive from homozygous mutant germ-line clones, and this provides a very powerful way to find mutants in maternally supplied components that are essential for embryonic development⁵⁸. Although the ovo gene is on the X chromosome, Chou and Perrimon have generated a set of transgenic lines that carry the mutant form of the gene and a proximal FRT site on each of the four major autosomal chromosome arms⁵⁵. This makes it possible to use the DFS technique to do germ-line clone screens of most of the genome. hs, heat shock; m, mutation; w, white gene.

Please close this window to return to the main article.

Note: some figures may render poorly in a web browser. In such cases, please see the associated PDF file.