Which best describes DNA? A. a molecule that looks like a twisted ladder
B. both answers about DNA are correct
C. a molecule present in all living things

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.

All living organisms are composed of a. only one cell. b. at least 100 cells. c. at least three cells. d. one or more cells.

What is a traditional chinese touch therapy involving finger pressure applied to specific areas of the body to restore the flow of qi.