In the absence of lactose, the repressor protein encoded by the I gene binds to the lac operator and prevents transcription. Binding of allolactose to the repressor causes it to leave the operator. This enables RNA polymerase to transcribe the three genes of the operon.
A tough-skinned tropical fruit, the mango features a sweet, orange- to red-color flesh inside when ripe. Kensington pride, Kent, Palmer and sensation are only a few of the many varieties of mango available through groceries and markets.
However, I think 'soft' is an incorrect term. I think a better description might be firm, but yields slightly when pressed.. By the time a mango is truly soft, it is definitely over ripe by then and well on its way to rotting. A green (or unripened) mango will be hard and not yield at all when, when pressed. Green mango: Ripe mango.