A mutant strain of Salmonella bacteria carries a mutation of the rho protein that has full activity at 37°C but is completely inactivated when the mutant strain is grown at 40°C. Are all mRNAs affected by the rho protein mutation in the same way? Why or why not?
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
10. Transcription
Transcription in Prokaryotes
Problem 29c
Textbook Question
The DNA sequence below gives the first 12 base pairs of the transcribed region of a gene, and the template and nontemplate strands of DNA are identified. The transcription start is the thymine nucleotide at the end of the sequence given. Use the diagram to answer the list of questions. Make a copy of the diagram before you begin answering the questions, or have one group member diagram the answers for bacteria and another group member diagram the answers for eukaryotes. Nontemplate strand ___________TTGCTACGGTCA___________
Template strand ___________ AACGATGCCAGT___________
Assuming the sequence shown is part of a bacterial gene, draw the approximate positions of the promoter sequence and the termination sequence.

1
Understand the structure of the DNA strands: The nontemplate strand (also called the coding strand) has the same sequence as the RNA transcript (except thymine is replaced with uracil in RNA). The template strand is complementary to the RNA transcript and is used by RNA polymerase during transcription.
Identify the transcription start site: The problem states that transcription starts at the thymine nucleotide at the end of the sequence. This means the RNA polymerase will begin synthesizing RNA from the complementary adenine on the template strand.
Locate the promoter sequence: In bacterial genes, the promoter is typically located upstream of the transcription start site. The -10 region (Pribnow box) often has the consensus sequence TATAAT, and the -35 region has the consensus sequence TTGACA. Approximate their positions relative to the transcription start site on the nontemplate strand.
Determine the termination sequence: In bacteria, termination sequences can be rho-dependent or rho-independent. Rho-independent termination often involves a GC-rich region followed by a series of uracils in the RNA transcript. Look for a potential GC-rich region and a poly-T sequence on the template strand, as these would correspond to the termination signal.
Diagram the positions: On the nontemplate strand, mark the approximate locations of the promoter (-10 and -35 regions) upstream of the transcription start site and the termination sequence downstream of the transcribed region. Ensure the diagram reflects the bacterial gene structure.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Transcription in Prokaryotes
Transcription in prokaryotes occurs in the cytoplasm and involves the synthesis of RNA from a DNA template. The process begins at a promoter region, where RNA polymerase binds to initiate transcription. In bacteria, the promoter is typically located upstream of the gene, and transcription continues until a termination signal is reached, resulting in the production of a messenger RNA (mRNA) molecule.
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Prokaryotic Transcription
Promoter and Terminator Sequences
Promoter sequences are specific DNA regions that signal the start of transcription, usually containing consensus sequences recognized by RNA polymerase. In contrast, terminator sequences signal the end of transcription, causing RNA polymerase to detach from the DNA. Understanding the locations of these sequences is crucial for mapping the transcriptional unit of a gene.
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Sequencing Difficulties
Nontemplate and Template Strands
In DNA, the nontemplate strand (also known as the coding strand) has the same sequence as the RNA transcript (except for thymine being replaced by uracil), while the template strand is complementary to the RNA. During transcription, RNA polymerase reads the template strand to synthesize RNA, making it essential to identify both strands when analyzing gene expression and transcriptional processes.
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Double Strand Breaks
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