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.
Press the skin. Press the papaya gently with your fingertips. If the fruit is ripe, your fingers should sink slightly into it, similar to a ripe avocado. A hard papaya is not ripe. A papaya with mushy spots or shriveled areas is overripe, Avoid papayas with soft flesh near the stem end.