If a cell contains a nucleus, it must be a(n)

plant cell
eukaryotic cell
animal cell
prokaryotic cell

What is thought to have caused the mass extinction at the end of the cretaceous period?

All but one describes an effect of aging on the digestive system. a) decreased acid secretion b) decreased elasticity of stomach c) capacity to resist damage decreases d) food remains in stomach for less time

Restriction enzymes are used in making recombinant dna. describe the role restriction enzymes perform when constructing recombinant dna.