Occasionally, some lethal allele (like sickle cell) is unusually common (more than 50% heterozygotes). what does this tell us?

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.