After a cardiac muscle contracts, what chemical reaction is needed to prepare the muscle cells for the next contraction

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.

As a small change in a person's dna can cause a genetic disorder

Explain why the plants cortex would serve as the best food source for animals