Gerald Rubin and Allan Spradling devised a method of introducing
a transposon into Drosophila. This approach has been important
for the transposon tagging of many Drosophila genes. The
researchers began with a P element that had been cloned on a plasmid.
Using cloning methods, they inserted the wild-type allele for the rosy
gene into the P element in this plasmid. The recessive allele, rosy,
results in a rosy eye color, while the wild-type allele, rosy+, produces
red eyes. The plasmid also had an intact transposase gene.
The cloned DNA is shown to the right.
Rubin and Spradling used a micropipette to inject this DNA
into regions of embryos that would later become reproductive
cells. These embryos were originally homozygous for the recessive
rosy allele. However, the P element carrying the rosy+ allele could “hop” out of the plasmid and into a chromosome of the cells that were destined to become germ cells (i.e., sperm or egg cells). After the embryos had matured to adults, the flies were then mated to flies that were homozygous for the recessive rosy allele. If offspring inherited a chromosome carrying the P element with the rosy+ gene, those offspring would have red eyes. Therefore, the
that had a P element insertion.
Now here is the question. Let’s suppose you were interested in
identifying genes that play a role in wing development. Outline the
experimental steps you would follow, using the plasmid with the P
element containing the rosy+ gene, as a way to transposon tag
genes that play a role in wing development. (Note: You should assume
that the inactivation of a gene involved in wing development
would cause an abnormality in wing shape. Also keep in mind that
most P element insertions inactivate genes and may be inherited in
a recessive manner.)
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