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Ch.11 Nucleic Acids Big Molecules with a Big Role
Frost - General, Organic and Biological Chemistry 4th Edition
Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoFrost 4th EditionCh.11 Nucleic Acids Big Molecules with a Big RoleProblema 76a
Capitolo 7, Problema 76a

A base substitution changes a codon for an enzyme from GCC to GCA. Why is there no change in the amino acid order in the protein?

Guida verificata passo dopo passo
1
Understand the concept of codons: Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. Each codon is matched to an amino acid based on the genetic code.
Examine the codon change: The problem states that the codon changes from GCC to GCA. Both codons are sequences of nucleotides that represent specific amino acids.
Refer to the genetic code table: Use a genetic code table to determine which amino acid corresponds to GCC and GCA. Both GCC and GCA code for the amino acid alanine, as the genetic code is degenerate (multiple codons can code for the same amino acid).
Explain the concept of degeneracy: The genetic code is degenerate, meaning that some amino acids are encoded by more than one codon. This redundancy ensures that certain mutations, such as base substitutions, do not always result in a change in the amino acid sequence.
Conclude why there is no change: Since both GCC and GCA code for alanine, the base substitution does not alter the amino acid sequence in the protein. This is an example of a silent mutation, where the change in the nucleotide sequence does not affect the protein's structure or function.

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Codon Redundancy

Codon redundancy, also known as the genetic code's degeneracy, refers to the phenomenon where multiple codons can code for the same amino acid. In this case, both GCC and GCA code for the amino acid alanine, meaning that a base substitution from GCC to GCA does not alter the resulting protein's amino acid sequence.
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03:25
The Genetic Code Concept 1

Amino Acids and Proteins

Amino acids are the building blocks of proteins, and the sequence of amino acids determines a protein's structure and function. The genetic code translates sequences of nucleotides in DNA into specific amino acids, which are linked together to form proteins. Understanding this relationship is crucial for grasping how changes in DNA can affect protein synthesis.
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2:21
Amino Acid Catabolism: Amino Group Concept 1

Base Substitution Mutation

A base substitution mutation occurs when one nucleotide in the DNA sequence is replaced by another. This type of mutation can lead to changes in the corresponding mRNA and potentially alter the amino acid sequence of a protein. However, due to codon redundancy, some base substitutions do not result in any change to the amino acid sequence, as seen in the example provided.
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5:07
Naming Alkanes with Substituents Example 1
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Domanda del libro di testo

What is the one-letter amino acid sequence formed from the following mRNA that codes for a pentapeptide that is an endorphin called Met-enkephalin?

5'AUG|UAC|GGU|GGA|UUU|AUG|UAA3'

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Provide the three-letter amino acid sequence expected from each of the following mRNA segments:

b. 5'CUA|AGC|UUC|AAC|UGG3'

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What is the anticodon on tRNA for each of the following codons in an mRNA?

c. GAA

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In sickle-cell anemia, a base substitution in the hemoglobin gene replaces glutamate (a polar amino acid) with valine. Why does the replacement of one amino acid cause such a drastic change in biological function?

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Provide a reason why there is no vaccine for the common cold.

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A base substitution for an enzyme replaces leucine (a nonpolar amino acid) with alanine. Why does this change in amino acids have little effect on the biological activity of the enzyme?