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Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 11 - Gene Mutation, DNA Repair, and Homologous RecombinationProblem 41b
Chapter 11, Problem 41b

The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.
DNA sequencing gels showing wild-type and mutant segments, highlighting differences in nucleotide sequences.
Identify the template and nontemplate strands of DNA.

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1
Examine the DNA sequencing gels provided for both the wild-type and mutant segments. Identify the sequence of nucleotides for each strand based on the dideoxynucleotide termination method.
Determine the sequence of the mRNA by transcribing the DNA strand that serves as the template. Remember that RNA uses uracil (U) instead of thymine (T).
Identify the complementary strand to the template strand. This strand is the nontemplate strand, which matches the mRNA sequence (except for T in DNA being replaced by U in RNA).
Locate the start codon (AUG) in the mRNA sequence and verify the next five codons to ensure the sequence corresponds to the N-terminal end of the protein.
Confirm the orientation of the template and nontemplate strands by comparing the sequences derived from the gels and ensuring they align with the transcription and translation processes.

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Key Concepts

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

Template and Nontemplate Strands

In DNA, the template strand is the one that serves as a guide for RNA synthesis during transcription, while the nontemplate strand, also known as the coding strand, has the same sequence as the RNA produced (except for thymine being replaced by uracil). Understanding which strand is which is crucial for interpreting sequencing data, as it determines the direction of transcription and the corresponding amino acid sequence.
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Dideoxynucleotide Sequencing

Dideoxynucleotide sequencing, or Sanger sequencing, is a method used to determine the nucleotide sequence of DNA. It involves incorporating dideoxynucleotides, which terminate DNA strand elongation, allowing for the generation of fragments of varying lengths that can be separated by gel electrophoresis. This technique is essential for analyzing the specific sequences of both wild-type and mutant DNA segments.
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Codons and Start Codon

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. The start codon, typically AUG, signals the beginning of translation and is crucial for the correct assembly of the protein. Identifying the start codon and subsequent codons in the sequenced DNA is vital for understanding the functional implications of mutations in the protein-coding region.
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Related Practice
Textbook Question

Common baker's yeast (Saccharomyces cerevisiae) is normally grown at 37°C, but it will grow actively at temperatures down to approximately 25°C. A haploid culture of wild-type yeast is mutagenized with EMS. Cells from the mutagenized culture are spread on a complete-medium plate and grown at 25°C. Six colonies (1 to 6) are selected from the original complete-medium plate and transferred to two fresh complete-medium plates. The new complete plates (shown) are grown at 25°C and 37°C. Four replica plates are made onto minimal medium or minimal plus adenine from the 25°C complete-medium plate. The new plates are grown at either 25°C or 37°C and the growth results are shown.

Classify the nature of the mutations in colonies 1, 2, and 5.

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Textbook Question

Common baker's yeast (Saccharomyces cerevisiae) is normally grown at 37°C, but it will grow actively at temperatures down to approximately 25°C. A haploid culture of wild-type yeast is mutagenized with EMS. Cells from the mutagenized culture are spread on a complete-medium plate and grown at 25°C. Six colonies (1 to 6) are selected from the original complete-medium plate and transferred to two fresh complete-medium plates. The new complete plates (shown) are grown at 25°C and 37°C. Four replica plates are made onto minimal medium or minimal plus adenine from the 25°C complete-medium plate. The new plates are grown at either 25°C or 37°C and the growth results are shown.

What can you say about colony 4?

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Textbook Question

The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.

Write the DNA sequence of both alleles, including strand polarity.

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Textbook Question

The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.

Write out the mRNA sequences encoded by each template strand, and underline the start codons.

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Textbook Question

The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.

Determine the amino acid sequences translated from these mRNAs.

582
views
Textbook Question

The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.

What is the cause of the mutation?

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