There are several reasons why you may want to remobilize a P-element in a particular line. You may have a P-element insertion line with an insertion in an area of the chromosomes that is of interest to you. If the line has no visible phenotype or if you find that it lies just outside of the area you are interest in you may want to remobilize the P-element so that it inserts in the desired area. Targeted jumps are not possible (you can't get P-elements to go to a particular place on the chromosomes) but you can allow it to jump around and then search for new insertion lines with the desired insertion. Usually, when P-elements jump they jump only a short distance (less than 1 kb) but longer jumps and jumps to new chromosomes are also possible. The series of genetic crosses below represent a jump-start scheme for a P-element on the second chromosome.
Start with males that have the P-element insertion. If possible it is easier
to start with lines that are homozygous for P-element insertion. This is, of
course, not possible if the insertion is recessive lethal. Cross these flies
with a P-element insertion to virgin females from a line of flies that has an
active transposase gene. The transposase gene (symbolized by 
2-3)
does not have a visible phenotype but it is linked genetically to a mutant stubble
locus. Therefore, the mutant stubble phenotype, (bristles on the thorax that
look like they have been shaved off and are growing back) can be used as a marker
for the transposase gene.
Crosses for a Second Chromosome Jump-Start
|
yw/>; P/P; +/+
|
X
|
yw/yw; BcElp/CyO;Sb(
2-3)/Ser |
From this cross chose red-eyed males with curly wings and stubble bristles. What would the genotype of these flies be?