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Chapter 15 The genetic code is almost universal. Why do you think it is nearly universal? (Page 282) Answer: The very strong similarity among organisms indicates a common ancestry of the code. It is widely accepted that RNA polymerase has no proofreading capacity. Would you expect high or low levels of error in transcription as compared with DNA replication? Why do you think it is more important for DNA polymerase than for RNA polymerase to proofread? (Page 283) Answer: One would expect higher amounts of error in transcription over DNA replication. Proofreading is important in DNA replication because errors in DNA replication will be passed on to offspring as mutations. However, RNA's have very short life spans in the cytoplasm therefore mistakes are not permanent. The lack of proofreading allows for faster transcription. The prokaryotic promoter has two distinct elements that are not identical. How is this important to the initiation of transcription? (Page 285) Answer: The promoter acts a binding site for RNA polymerase. The structure of the promoter provides information as to both where to bind, but also the direction of transcription. If the two sites were identical, the polymerase would need some other cue for the direction of transcription. How can the same gene encode different transcripts? (Figure 15.11) Answer: Splicing can produce multiple transcripts from the same gene. How is the wobble phenomenon related to the number of tRNAs and the degeneracy of the genetic code? (Figure 15.19) Answer: Wobble not only explains the number of tRNAs that are observed due to the increased flexibility in the 5’ position, it also accounts for the degeneracy that is observed in the Genetic Code. The degenerate base is the one in the wobble position.