A double helical structure where two strands of DNA run antiparallel to
each other. How does this structure cause the number of
purines to equal the number of pyrimidines as observed by
Chargaff?

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.

Write a paragraph at least 5 sentences “why all vaccinations should be mandatory”

Aplant may open end close its stomata to prevent excess water loss and maintain