The lac operon in e. coli consists of genes that code for enzymes necessary for the breakdown of lactose. when lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. when lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. in the absence of glucose (a preferred energy source for bacteria), the protein cap binds to a regulatory site near the lac promoter to activate transcription of the lac operon.

The dna in a cell’s nucleus encodes proteins that are eventually targeted to every membrane and compartment in the cell, as well as proteins that are targeted for secretion from the cell. for example, consider these two proteins: phosphofructokinase (pfk) is an enzyme that functions in the cytoplasm during glycolysis. insulin, a protein that regulates blood sugar levels, is secreted from specialized pancreatic cells. assume that you can track the cellular locations of these two proteins from the time that translation is complete until the proteins reach their final destinations. for each protein, identify its targeting pathway: the sequence of cellular locations in which the protein is found from when translation is complete until it reaches its final (functional) destination. (note that if an organelle is listed in a pathway, the location implied is inside the organelle, not in the membrane that surrounds the organelle.)

And give a detailed description! scientist observes the boundary between two tectonic plates for a decade and finds that no new volcanoes have formed over the course of her investigation. does this result support the theory of plate tectonics? why or why not?

Crossing over and independent assortment are important activities that occur during meiosis. what is the significance of these activities