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.
Do not jab into the fruit, rather push on the skin with the pad of your thumb or finger. Watch and feel how the skin of the mango reacts. If the skin gives a small bit rather than being hard to the touch, then the mango is near or at the point of being ripe. Smell the stem end of the mango. Hold the end of the mango, where the stem was attached, up to your nose. If the fruit is ripe there will be a fruity aroma. If not, the mango is probably not yet ripe. Place a mango that is hard to the touch or has no aroma in a bowl with ripening bananas or other fruit. Allow the mango to sit for a day or so and test again for ripeness. Do not attempt to judge the ripeness of a mango by the color of the skin.