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CHAPTER 14 Concept check questions (in figure legends) FIGURE 14.2 Concept check: If a mutation changed the start codon into a stop codon, would this mutation affect the length of the RNA? Explain. Answer: The mutation would not affect the length of the RNA, because it would not terminate transcription. However, the encoded polypeptide would be shorter. FIGURE 14.5 Concept check: What does the term “consensus sequence” mean? Answer: When comparing a group of related sequences, the consensus sequence is the most common base found at each location within that sequence. FIGURE 14.6 Concept check: Why is it necessary for portions of the sigma () factor protein to fit into the major groove? Answer: Parts of sigma factor must fit into the major groove so it can recognize a base sequence of a promoter. FIGURE 14.7 Concept check: What feature of the -10 sequence makes it easy to unwind? Answer: The -10 is AT rich, which has fewer hydrogen bonds compared to a region with a lot of GC base pairs FIGURE 14.10 Concept check: What would be the consequences if a mutation removed the rut site from this RNA molecule? Answer: The mutation would prevent -dependent termination of transcription. FIGURE 14.11 Concept check: Why is NusA important for this process? Answer: NusA helps RNA polymerase to pause, which facilitates transcriptional termination. FIGURE 14.13 Concept check: What is the functional role of the TATA box? Answer: The TATA box provides a precise starting point for the transcription of eukaryotic structural genes. FIGURE 14.14 Concept check: Why is CTD phosphorylation functionally important? Answer: The phosphorylation of CTD allows RNA polymerase to proceed to the elongation phase of transcription. FIGURE 14.17 Concept check: What is the difference between an endonuclease and an exonuclease? Answer: An endonuclease can cleave within a strand, whereas an exonuclease digests a strand, one nucleotide at a time, starting at one end. FIGURE 14.18 Concept check: Which of these three mechanisms is very common in eukaryotes? Answer: Splicing via a spliceosome is very common in eukaryotes. FIGURE 14.20 Concept check: Describe the roles of snRNPs in the splicing process. Answer: snRNPs are involved in recognizing the intron boundaries, cutting out the intron, and connecting the two adjacent exons together. FIGURE 14.21 Concept check: What are three functional roles of the 7-methlyguanosine cap? Answer: The 7-methylguanosine cap is important for the proper splicing of pre-mRNA, the exit of mRNA from the nucleus, and the binding of mRNA to a ribosome. FIGURE 14.23 Concept check: What is a functional consequence of RNA editing? Answer: The consequence of RNA editing is that the amino acid sequence of an encoded polypeptide may be changed, which can affect its function.