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
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

10. Transcription

Transcription in Prokaryotes

Genetics

10. Transcription

Transcription in Prokaryotes

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3:25 minutes

Problem 12

Textbook Question

Draw a bacterial promoter and label its consensus sequences. How does this promoter differ from a eukaryotic promoter transcribed:
By RNA polymerase II?
By RNA polymerase I?
By RNA polymerase III?

Verified step by step guidance

Start by drawing a bacterial promoter. A bacterial promoter typically consists of two key consensus sequences: the -10 sequence (Pribnow box) and the -35 sequence. Label these sequences on your drawing. The -10 sequence is usually 'TATAAT', and the -35 sequence is typically 'TTGACA'.

Indicate the transcription start site (+1) on your drawing. This is the point where RNA polymerase begins transcription. The -10 and -35 sequences are located upstream of this site, with the -10 sequence closer to the transcription start site.

Explain how the bacterial promoter differs from a eukaryotic promoter transcribed by RNA polymerase II. Eukaryotic promoters often contain a TATA box (similar to the -10 sequence in bacteria) but also include additional regulatory elements such as enhancers and silencers. These elements can be located far from the transcription start site, unlike bacterial promoters.

Describe the differences between bacterial promoters and those transcribed by RNA polymerase I. RNA polymerase I transcribes rRNA genes, and its promoters are specialized, containing core promoter elements and upstream control elements (UCEs) that are distinct from bacterial promoter sequences.

Discuss the differences between bacterial promoters and those transcribed by RNA polymerase III. RNA polymerase III transcribes tRNA and 5S rRNA genes, and its promoters are often located within the transcribed region (internal promoters), which is a key distinction from bacterial promoters that are entirely upstream of the transcription start site.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Bacterial Promoter Structure

A bacterial promoter is a specific DNA sequence that initiates transcription in prokaryotes. It typically contains consensus sequences such as the -10 (Pribnow box) and -35 regions, which are recognized by RNA polymerase. These sequences are crucial for the binding of the transcription machinery and the subsequent initiation of RNA synthesis.

Eukaryotic Promoter Variability

Eukaryotic promoters are more complex than bacterial promoters and can vary significantly between different RNA polymerases. For instance, RNA polymerase II promoters often include a TATA box and other regulatory elements, while RNA polymerase I and III promoters have distinct sequences and structures that facilitate the transcription of rRNA and tRNA, respectively. This complexity allows for greater regulation of gene expression in eukaryotes.

Transcription Factors and Regulation

In eukaryotes, transcription factors play a critical role in the binding of RNA polymerase to the promoter. These proteins can enhance or inhibit transcription by interacting with specific DNA sequences and the transcription machinery. This regulatory mechanism is essential for the precise control of gene expression in response to various cellular signals, distinguishing it from the simpler regulation seen in prokaryotes.

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Related Practice

Textbook Question

The diagram below shows a DNA duplex. The template strand is identified, as is the location of the nucleotide.

Assume this region contains a gene transcribed in a bacterium. Identify the location of promoter consensus sequences and of the transcription termination sequence.

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Textbook Question

The DNA sequences shown below are from the promoter regions of six bacterial genes. In each case, the last nucleotide in the sequence (highlighted in blue) is the nucleotide that initiates transcription. Determine the consensus sequence for the Pribnow box from these sequences.

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Textbook Question

Bacterial and eukaryotic gene transcripts can differ—in the transcripts themselves, in whether the transcripts are modified before translation, and in how the transcripts are modified. For each of these three areas of contrast, describe what the differences are and why the differences exist.

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Textbook Question

Describe the two types of transcription termination found in bacterial genes. How does transcription termination differ for eukaryotic genes?

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Textbook Question

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following:

3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5'

5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3'

Label the template and coding DNA strands.

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Textbook Question

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following:

3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5'

5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3' Draw the mRNA structure that forms during transcription of this segment of the TrpA gene.

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Textbook Question

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following:

3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5'

5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3'

Explain how a sequence of this type leads to intrinsic termination of transcription.

466

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Textbook Question

Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?

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Draw a bacterial promoter and label its consensus sequences. How does this promoter differ from a eukaryotic promoter transcribed:By RNA polymerase II? By RNA polymerase I? By RNA polymerase III?

Key Concepts

Bacterial Promoter Structure

Eukaryotic Promoter Variability

Transcription Factors and Regulation

Watch next

Draw a bacterial promoter and label its consensus sequences. How does this promoter differ from a eukaryotic promoter transcribed:
By RNA polymerase II?
By RNA polymerase I?
By RNA polymerase III?