Question

A mutation removes a single base pair within the coding sequence of a gene and inactivates the protein encoded by the gene. Such a mutation is a. a silent mutation. b. a missense mutation. c. a nonsense mutation. d. a frameshift mutation. e. both b and c.

Short answer

The mutation described in the problem is a frameshift mutation. Therefore, the correct answer is (d) a frameshift mutation.

Step-by-step solution

Understand the types of mutations

Genetic mutations can be classified into different types. A silent mutation doesn't change the amino acid sequence of a protein. A missense mutation changes one amino acid in a protein, altering the protein's function. A nonsense mutation prematurely stops the production of a protein, rendering it nonfunctional. A frameshift mutation, which results from the addition or deletion of a base pair, significantly alters the reading frame, resulting in a vastly different and often nonfunctional protein.

Identify the type of mutation described

According to the question, there is a mutation that removes a single base pair within the coding sequence of a gene and deactivates the protein. This type of mutation changes the reading frame, resulting in a frameshift mutation.

Select the correct option

Based on the understanding of genetic mutations, the mutation described in the problem is a frameshift mutation. Therefore, the correct option is (d) a frameshift mutation.

Key concepts

Silent Mutation

Silent mutations are a fascinating aspect of genetic mutations. These occur when a change in the DNA sequence does not affect the protein being produced. This happens because of the redundancy of the genetic code, where multiple DNA codons can specify the same amino acid.

For example, the DNA sequences "GAA" and "GAG" both code for the amino acid glutamate.

• No change in protein function
• Often occurs in the third base of the codon
• Does not alter protein efficacy or behavior

Silent mutations are like editing a text but ending up with the same message. Understanding them helps in comprehending how genetic coding is robust against some mutations.

Missense Mutation

Missense mutations result in the substitution of one amino acid for another in a protein sequence. This is due to a single nucleotide change in the DNA, causing one incorrect protein to be synthesized.

The impact of a missense mutation can vary:

• Minor if the new amino acid is similar to the original
• Severe if it changes the protein's active site or stability

An example includes sickle cell anemia, where a small change can have dramatic effects. Understanding missense mutations helps identify how gene alterations can lead to different traits or diseases.

Nonsense Mutation

Nonsense mutations are a type of mutation that introduces a premature stop codon in the DNA sequence. This results in a shortened, typically nonfunctional protein.

Key points to consider:

• Leads to a shorter amino acid chain or truncated protein
• Usually results in loss of protein function
• Can cause genetic diseases like cystic fibrosis

The word "nonsense" in this context highlights how the mutation in question renders the sequence gibberish beyond a certain point, halting protein production prematurely.

Frameshift Mutation

Frameshift mutations occur when base pairs are inserted into or deleted from the DNA sequence. Such changes affect the reading frame, altering every amino acid coded thereafter.

They typically happen due to:

• Insertion or deletion of non-multiples of three nucleotides
• Dramatic shift in protein sequence

This shift can render the protein nonfunctional and often results in severe genetic disorders. The analogy would be skipping or repeating a word in a sentence, scrambling its meaning. Frameshift mutations illustrate the delicate balance of genetic coding and how small disruptions can lead to significant effects.