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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2:37 minutes

Problem 5a

Textbook Question

The following is a portion of an mRNA sequence:
3'-AUCGUCAUGCAGA-5'
During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

Verified step by step guidance

Determine the directionality of the mRNA sequence provided. mRNA sequences are conventionally written in the 5' to 3' direction. However, the sequence given is written in the 3' to 5' direction, so it must be reversed to analyze transcription properly.

Reverse the sequence to convert it into the 5' to 3' direction. The reversed sequence becomes 5'-AUGCAGAUCGUA-3'.

Recall that during transcription, RNA is synthesized in the 5' to 3' direction, meaning the RNA polymerase adds nucleotides to the 3' end of the growing mRNA strand.

Identify the template strand of DNA that would have been used to produce this mRNA. The template strand is complementary and antiparallel to the mRNA. For the reversed mRNA sequence (5'-AUGCAGAUCGUA-3'), the template DNA strand would be 3'-TACGTCTAGCAT-5'.

Analyze the position of the adenine (A) at the left-hand side of the original sequence. Since transcription proceeds from the 3' end of the template DNA strand to the 5' end, the adenine at the left-hand side of the original sequence (3'-AUCGUCAUGCAGA-5') would have been the last nucleotide added during transcription.

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Key Concepts

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

Transcription Process

Transcription is the process by which a segment of DNA is copied into mRNA by the enzyme RNA polymerase. During this process, RNA polymerase reads the DNA template strand and synthesizes a complementary RNA strand. The direction of synthesis is 5' to 3', meaning that nucleotides are added to the 3' end of the growing mRNA strand.

mRNA Orientation

mRNA is synthesized in a specific orientation, with the 5' end being the start of the molecule and the 3' end being the end. The sequence provided in the question is written in the 3' to 5' direction, which indicates that the actual synthesis of mRNA would have occurred in the 5' to 3' direction. This orientation is crucial for understanding which nucleotide was added first.

Nucleotide Addition

During mRNA synthesis, nucleotides are added one at a time to the growing chain. The first nucleotide added corresponds to the first nucleotide of the mRNA sequence, which is determined by the template DNA strand. In the given sequence, the adenine at the left-hand side (3' end) of the mRNA is the last nucleotide added, as it is the 3' end of the synthesized strand.

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Textbook Question

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

If this region is a eukaryotic gene transcribed by RNA polymerase III, where are the promoter consensus sequences located?

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Textbook Question

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

Assume this region contains a gene transcribed to form mRNA in a eukaryote. Identify the location of the most common promoter.

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Textbook Question

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

Identify the direction in which the promoter region for this gene will be located.

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Textbook Question

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

Write out the sequence and polarity of the DNA duplex that encodes this mRNA segment. Label the template and coding DNA strands.

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Textbook Question

Compare and contrast the properties of DNA polymerase and RNA polymerase, listing at least three similarities and at least three differences between the molecules.

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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.

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Textbook Question

Describe the difference between introns and exons.

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