Table 1.

Strain types in the P-M system

P susceptibility high: >10%GD low: <10%GD	P inducibility low: <10%GD high: >10%GD	strain type
high	low	M’
low	low	Q
low	high	P
high	low	M (P-elements (−))

Drosophila melanogaster is divided into the four strain types by GD ratios. P susceptibility shows the regulatory capacity against the P-elements and P inducibility exhibits the ability to transpose P-elements in progeny