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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
Chapter 11, Problem 19b

Using the adenine–thymine base pair in this DNA sequence
...GCTC...
...CGAG...
Give the sequence after a transversion mutation.

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1
Identify the original DNA sequence provided in the problem. In this case, the sequence is shown as two complementary strands: 'CCTTAGGATTCC' and 'GGAATCCTTAAGG'.
Understand the concept of a transversion mutation. A transversion mutation occurs when a purine (adenine or guanine) is replaced by a pyrimidine (cytosine or thymine), or vice versa.
Locate the site of the mutation in the sequence. From the image, the mutation occurs in the second strand where 'G' is replaced by 'C'. This change also affects the complementary strand, where 'C' is replaced by 'G'.
Update the sequence to reflect the transversion mutation. Replace the affected base pair in both strands: 'CCTTAGGATTCC' becomes 'CCTTAGGAGTCC', and 'GGAATCCTTAAGG' becomes 'GGAATCCTCAGG'.
Verify that the new sequence maintains proper base pairing rules (adenine pairs with thymine, and guanine pairs with cytosine) after the mutation. Ensure the complementary strand reflects the change accurately.

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Key Concepts

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

Transversion Mutation

A transversion mutation is a type of point mutation where a purine base (adenine or guanine) is replaced by a pyrimidine base (cytosine or thymine), or vice versa. This contrasts with transitions, where a purine is replaced by another purine or a pyrimidine by another pyrimidine. Transversions can lead to significant changes in the protein sequence, potentially altering the function of the resulting protein.
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DNA Base Pairing

DNA base pairing refers to the specific pairing of nitrogenous bases in the DNA double helix, where adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C). This complementary base pairing is crucial for DNA replication and transcription, ensuring that genetic information is accurately copied and expressed. Understanding base pairing is essential for predicting the effects of mutations on DNA sequences.
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Effects of Mutations on Protein Synthesis

Mutations can have various effects on protein synthesis, ranging from silent mutations that do not change the amino acid sequence to missense mutations that result in a different amino acid being incorporated. In some cases, mutations can lead to nonsense mutations, creating premature stop codons that truncate the protein. The specific impact of a mutation depends on its nature and location within the gene, influencing the overall function of the protein produced.
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