Which of these statements about light microscopes and electron microscopes is not true?
a. you can use light microscopes to observe both living and nonliving cells; you can use electron microscopes to observe only nonliving cells.
b. light microscopes use visible light rays; electron microscopes use beams of electrons.
c. preserving and staining samples for use with light microscopes is necessary; preserving and staining samples for use with electron microscopes is optional.

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.

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays

14. which of the following codons code for threonine? a. ucg b. ugu c. cga d. aca