Why do translocation sometimes reduces the total number of chromosomes

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

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?

Anurse is in the dining room and overhears a new nurse tell a client with body dysmorphic disorder that she's much too thin and must eat more before she can go home. the client bursts into tears and runs out of the dining room. what is the best way for the nurse to address this situation?