Which of the following are common features of expression vectors?
a. small segments of dna that encode tags for protein purification.
b. transcriptional start and stop sites
c. a tightly controlled promoter than can only be induced under certain circumstances
d. antibiotic resistance gene
e. all of the above are common features of expression vectors

Metamorphic rocks are formed when sedimentary or igneous rocks are subjected to heat or pressure and recrystallize without melting. which of the following rocks results from the metamorphism of limestone? a. granite b. slate c. sandstone d. marble

What is involved in redox reactions

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.