1. Fig. 12-2, p.187

2. Fig. 12-5, p.190

3. Fig. 12-6, p.191 2-nanometer diameter overall 0.34-nanometer distance between each pair of bases 3.4-nanometer length of each full twist of the double helix In all respects shown here, the Watson–Crick model for DNA structure is consistent with the known biochemical and x-ray diffraction data. The pattern of base pairing (A with T, and G with C) is consistent with the known composition of DNA (A = T, and G = C).

4. Fig. 12-7, p.192

5. Fig. 12-8, p.192 new old

6. Fig. 12-9, p.193 Any gaps between bases of the “new” DNA are joined to form a continuous strand. The base sequence of each half-old, half-new DNA molecule is identical to that of the parent. Part of a parent DNA molecule, with two complementary strands of base-paired nucleotides. Replication starts. The strands are unwound at many sites along the molecule’s length. Each of the two parent strands guides the assembly of new DNA strands from free nucleotides, according to base-pairing rules.

7. Fig. 12-10, p.194

8. Fig. 13-2, p.198

9. Fig. 13-3, p.198

11. gene region RNA polymerase, the enzyme that catalyzes transcription DNA template unwinding newly forming RNA transcript DNA template winding up

12. Fig. 13-3, p.198

13. Table 13-1, p.199

14. Fig. 13-5, p.200

15. Fig. 13-7, p.201 amino acid attachment site anticodon

16. Fig. 13-8, p.202 mRNA initiator tRNA small ribosomal subunit large ribosomal subunit Initiation A mature mRNA leaves the nucleus and enters cytoplasm, which has many free amino acids, tRNAs, and ribosome subunits. An initiator tRNA binds to a small ribosomal subunit and the mRNA. A large ribosomal subunit joins, and the cluster is now called an initiation complex.

17. Fig. 13-8, p.202 A peptide bond forms between the second and third amino acids (here, valine and leucine). A peptide bond forms between the first two amino acids (here, methionine and valine). An initiator tRNA carries the amino acid methionine, so the first amino acid of the new polypeptide chain will be methionine. A second tRNA binds the second codon of the mRNA (here, that codon is GUG, so the tRNA that binds carries the amino acid valine). Elongation The first tRNA is released and the ribosome moves to the next codon in the mRNA. A third tRNA binds to the third codon of the mRNA (here, that codon is UUA, so the tRNA carries the amino acid leucine).

18. Fig. 13-8, p.202 A peptide bond forms between the third and fourth amino acids (here, leucine and glycine) The second RNA is released and the ribosome moves to the next codon. A fourth tRNA binds the fourth mRNA codon (here, that codon is GGG, so the tRNA carries the amino acid glycine). Steps d and e are repeated over and over until the ribosome encounters a STOP codon in the mRNA. The mRNA transcript and the new polypeptide chain are released from the ribosome. The two ribosomal subunits separate from each other. Translation is now complete. Either the chain will join the pool of proteins in the cytoplasm or it will enter rough ER of the endomembrane system (Section 4.8). Termination

19. Fig. 13-9, p.202 THREONINEPROLINEGLUTAMATE LYSINE THREONINEPROLINEGLUTAMATELYSINE THREONINEPROLINEARGININEGLYCINE VALINE deletion in DNA part of DNA mRNA transcribed from DNA resulting amino acid sequence base substitution in DNA altered mRNA altered amino acid sequence altered amino acid sequence altered mRNA

20. Fig. 13-11, p.206 mRNA Final protein cytoplasmic pools of amino acids, ribosomal subunits, and tRNAs Convergence of RNAs Transcription Assembly of RNA on unwound regions of DNA molecule At an intact ribosome, synthesis of a polypeptide chain at the binding sites for mRNA and tRNAs Translation mRNA processing mature tRNA ribosomal subunits mature mRNA transcripts proteins tRNA rRNA