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 Eukaryotes

Genetics

10. Transcription

Transcription in Eukaryotes

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1:50 minutes

Problem 14

Textbook Question

Three genes identified in the diagram as A, B, and C are transcribed from a region of DNA. The 5'-to-3' transcription of genes A and C elongates mRNA in the right-to-left direction, and transcription of gene B elongates mRNA in the left-to-right direction. For each gene, identify the coding strand by designating it as an 'upper strand' or 'lower strand' in the diagram.

Verified step by step guidance

Understand the concept of transcription: During transcription, the RNA polymerase reads the template strand of DNA in the 3'-to-5' direction to synthesize mRNA in the 5'-to-3' direction. The coding strand is the DNA strand that has the same sequence as the mRNA (except that thymine is replaced by uracil in RNA).

Analyze the direction of transcription for each gene: For genes A and C, transcription elongates mRNA in the right-to-left direction. For gene B, transcription elongates mRNA in the left-to-right direction.

Determine the template strand for each gene: The template strand is complementary to the mRNA strand. For genes A and C, since transcription occurs right-to-left, the lower strand must be the template strand. For gene B, since transcription occurs left-to-right, the upper strand must be the template strand.

Identify the coding strand for each gene: The coding strand is the strand opposite to the template strand. For genes A and C, the upper strand is the coding strand because the lower strand is the template strand. For gene B, the lower strand is the coding strand because the upper strand is the template strand.

Summarize the results: For gene A, the coding strand is the upper strand. For gene B, the coding strand is the lower strand. For gene C, the coding strand is the upper strand.

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Key Concepts

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

Transcription Directionality

Transcription directionality refers to the orientation in which RNA polymerase synthesizes mRNA from a DNA template. In eukaryotic cells, transcription occurs in the 5'-to-3' direction, meaning that nucleotides are added to the 3' end of the growing mRNA strand. This directionality is crucial for understanding which DNA strand serves as the template and how the resulting mRNA aligns with the coding sequence.

Coding and Template Strands

In the context of DNA transcription, the coding strand (also known as the sense strand) has the same sequence as the mRNA (except for uracil replacing thymine), while the template strand (antisense strand) is complementary to the mRNA. Identifying which strand is the coding strand is essential for determining the correct sequence of the mRNA produced during transcription, as it dictates the protein-coding potential of the gene.

Gene Orientation

Gene orientation refers to the arrangement of genes on a DNA molecule, which can be oriented in either direction. This orientation affects how transcription occurs, as genes can be transcribed from either the upper or lower strand of the DNA. Understanding gene orientation is vital for correctly identifying which strand corresponds to each gene's transcription direction, as seen in the question regarding genes A, B, and C.

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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. Examine these sequences and identify the Pribnow box sequence at approximately -10 for each promoter.

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Textbook Question

What is the role of enhancer sequences in transcription of eukaryotic genes? Speculate about why enhancers are not part of transcription of bacterial genes.

661

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Textbook Question

Describe the difference between introns and exons.

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Textbook Question

For a eukaryotic gene whose transcription requires the activity of an enhancer sequence, explain how proteins bound at the enhancer interact with RNA pol II and transcription factors bound at the promoter.

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Textbook Question

Compare the control of gene regulation in eukaryotes and bacteria at the level of initiation of transcription. How do the regulatory mechanisms work? What are the similarities and differences in these two types of organisms in terms of the specific components of the regulatory mechanisms?

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Textbook Question

The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.

Are intron regions single stranded or double stranded? Why?

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Textbook Question

The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.

Label the introns.

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Textbook Question

The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.

Illustrate the R-loop structure that would be seen with electron microscopy.

491

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