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.
Ripeness is indicated by a bright yellowgold color on the skin that at the very least should be present on the eyes around the base of the fruit. Though industry literature states that a fully ripe pineapple may be entirely green, ''mature green,'' it is also true that it may not be ripe. Buying a fully green pineapple is risky. The stem end of the fruit has the highest sugar content and is the ripest portion. The higher up that yellow color goes, the more evenly a pineapple will be flavored. That color, plus a pleasant, mild pineapple aroma at the base are the best guides to ripeness.