24. One amino acid directly involved in the purine biosynthetic pathway is:
(A) alanine.
(B) aspartate.
(C) glutamate.
(D) leucine.
(E) tryptophan.

24. One amino acid directly involved in the purine biosynthetic pathway is (A) alanine (B) aspartate (C) glutamate (D) leucine (E) tryptophan

24. One amino acid directly involved in the purine biosynthetic pathway is: (A)alanine. (B) aspartate. (C)glutamate. (D)leucine. (E) tryptophan

7. One amino acid directly involved in the purine biosynthetic pathway is:(A) alanine.(B)aspartate.(C) glutamate.(D) leucine.(E) tryptophan

25. The synthesis of purine and pyrimidine nucleotides differ in that: (A) ATP is required in the synthesis of purines but not in the synthesis of pyrimidines. (B) purine biosynthesis starts with the formation of PRPP, whereas pyrimidines incorporate the PRPP near the end of the pathway. (C) purine formation requires a THF derivative, whereas pyrimidine formation does not. (D) pyrimidine biosynthesis is tightly regulated in the cell, whereas purine biosynthesis is not. (E) pyrimidines go through many steps, adding a single carbon or nitrogen each time, whereas the basic skeleton for purines is formed by two main precursors.

26. In base-excision repair, the first enzyme to act is: (A) AP endonuclease. (B) Dam methylase. (C) DNA ligase. (D) DNA glycosylase. (E) DNA polymerase.

27. In homologous genetic recombination, RecA protein is involved in: (A) formation of Holliday intermediates and branch migration. (B) introduction of negative supercoils into the recombination products. (C) nicking the two duplex DNA molecules to initiate the reaction. (D) pairing a DNA strand from one duplex DNA molecule with sequences in another duplex, regardless of complementarity. (E) resolution of the Holliday intermediate.

28. The excision (splicing) of many group I introns requires, in addition to the primary transcript RNA: (A) a cytosine nucleoside or nucleotide and a protein enzyme. (B) a guanine nucleoside or nucleotide (only). (C) a protein enzyme only. (D) a small nuclear RNA and a protein enzyme. (E) ATP, NAD, and a protein enzyme.

29. The signal sequences that direct proteins to the nucleus are: (A) always at the amino terminus of the targeted protein. (B) cleaved after the protein arrives in the nucleus. (C) not located at the ends of the peptide, but in its interior. (D) glycosyl moieties containing mannose 6-phosphate residues. (E) the same as those that direct certain proteins to lysosomes.

30. In the protein synthesis, approximately how many NTPs must be converted to NDPs to incorporate one amino acid into a protein? (A) 0 (B) 1 (C) 2 (D) 4 (E) 8

1. Production efficiency occurs when production ________. (A)is at a point beyond the production possibilities frontier (B) is on the production possibilities frontier or inside it (C)is at any attainable point (D)is on the production possibilities frontier

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