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.
Give the mango a good whiff right around the stem area. If the fruit has a strong fruity, sweet smell, there is a good chance that it has fully ripened. Sniff the mango near the stem end. The odor will be strongest there, and you will get a more accurate idea of how the fruit actually smells.