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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.

The body is protected against harmful flu viruses by

Which of the following sex and generation combinations directly produces the pollen tube of angiosperms? a) male gametophyteb) female gametophytec) male sporophyted) female sporophyte