Which one of the following enzymes of nucleotide metabolism is correctly paired with its pharmacologic inhibitor?

a. dihydrofolate reductase—methotrexate

b. inosine monophosphate dehydrogenase—hydroxyurea

c. ribonucleotide reductase—5-fluorouracil

d. thymidylate synthase—allopurinol

e. xanthine oxidase—probenecid

Which of the following elements does soil need in the largest quantities to sustain plant life? a. copper b. iron c. nitrogen d. zinc

What best explains whether bromine (br) or neon (ne) is more likely to form a covalent bond? bromine forms covalent bonds because it has seven valence electrons, but neon has eight valence electrons and already fulfills the octet rule. bromine forms covalent bonds because it has many electron shells, but neon has only two electron shells and is tightly bound to its electrons. neon forms covalent bonds because it can share its valence electrons, but bromine has seven valence electrons and can gain only one more electron. neon forms covalent bonds because it has only two electron shells, but bromine has many electron shells and will lose electrons in order to fulfill the octet rule.

How many copies of genes do gametes have?