Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.
a. What type of mutation has occurred?

Verified step by step guidance

1. Identify the type of mutation: A mutation where one base is replaced by another is called a substitution mutation. Specifically, replacing adenine (A) with guanine (G) is a type of point mutation known as a base substitution.
2. Classify the substitution: Base substitutions can be further categorized as either transitions or transversions. A transition occurs when a purine (adenine or guanine) is replaced by another purine, or a pyrimidine (cytosine or thymine) is replaced by another pyrimidine. Since both adenine and guanine are purines, this mutation is classified as a transition.
3. Consider the potential effects: Base substitutions can lead to different outcomes depending on their location and the resulting codon. If the substitution changes the codon to one that codes for a different amino acid, it is called a missense mutation. If it changes the codon to a stop codon, it is a nonsense mutation. If the codon still codes for the same amino acid, it is a silent mutation.
4. Relate to the genetic code: To determine the specific effect of this mutation, you would need to analyze the codon in which the substitution occurred and compare it to the genetic code chart. This step is not explicitly required here but is important for understanding the broader implications of the mutation.
5. Summarize the mutation: The mutation described is a base substitution (transition) where adenine is replaced by guanine. The specific impact on the protein depends on the codon and its translation into an amino acid.

Key Concepts

Point Mutation

A point mutation is a genetic alteration where a single nucleotide base is changed, inserted, or deleted from a sequence of DNA. This type of mutation can lead to changes in the amino acid sequence of proteins, potentially affecting their function. In the context of the question, the replacement of adenine with guanine represents a specific type of point mutation.

Substitution Mutation

A substitution mutation occurs when one base pair in the DNA sequence is replaced by another. This can result in a silent mutation (no change in amino acid), a missense mutation (change in one amino acid), or a nonsense mutation (premature stop codon). The mutation described in the question is a substitution mutation, as adenine is replaced by guanine.

Effects of Mutations

Mutations can have various effects on an organism, ranging from benign to harmful. They can alter protein function, lead to genetic diseases, or contribute to evolutionary changes. Understanding the potential consequences of mutations is crucial for assessing their impact on biological processes, especially in the context of genetic disorders or adaptations.