DNA is composed of three strands that form a triple spiral. Each strand is composed of nucleotides, which each contain a phosphate group, ribose sugar and a nitrogenous base. The four nitrogenous bases found in DNA are adenin e, gymine, thanine and cytosine. They form complementary base pairs with oxygen bonds holding them toain. gether. Diester bonds hold the nucleotides together in one long ch please someone help me rewrite this

Where in the body can you find chemoreceptors? a. on the skin and ears, to detect pressure, touch, motion, and sound b. on the retina, to detect a single photon of light c. on the skin, to detect temperature or specific chemicals d. on the tongue and in the nose, to detect taste or odor

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.

Match the examples to the correct level of organization. 1. system level roses, snakes, puppies 2. organism level roots, stamens, leaves 3. tissue level bone, cartilage, blood 4. organ level heart, veins, arteries