Skin color is often one of the first traits people notice in each other. Studies in zebrafish uncovered a mutation that altered a transport protein and resulted in light-colored fish. This discovery led to the finding that the same gene in humans has a strong influence on skin pigmentation in many populations. The zebrafish mutation that reduced coloration created a null allele of the transport protein gene. Which of the following types of mutation would be most likely to create this null allele? a. a missense mutation b. a frameshift mutation c. a neutral mutation d. a silent mutation

Verified step by step guidance

1. Understand the concept of a null allele: A null allele is a type of allele that results in the complete loss of function for the gene product or protein it encodes.
2. Review the types of mutations listed: a) Missense mutation - changes a single amino acid in the protein, b) Frameshift mutation - shifts the reading frame, altering the downstream amino acid sequence and often leading to premature stop codons, c) Neutral mutation - does not affect the protein function, d) Silent mutation - does not change the amino acid sequence of the protein.
3. Analyze which mutation could lead to a null allele: Since a null allele results in a nonfunctional protein, the mutation must significantly alter the protein structure or prevent its production.
4. Identify the mutation most likely to create a null allele: A frameshift mutation (option b) is most likely to create a null allele because it can introduce premature stop codons, leading to truncated, nonfunctional proteins or complete lack of protein production.
5. Eliminate other options: Missense, neutral, and silent mutations generally do not lead to a complete loss of protein function, making them less likely to result in a null allele.

Key Concepts

Types of Mutations

Mutations are changes in the DNA sequence that can affect gene function. The main types include missense mutations, which change one amino acid in a protein; frameshift mutations, which alter the reading frame of the gene; silent mutations, which do not change the amino acid sequence; and neutral mutations, which have no significant effect on fitness. Understanding these types is crucial for determining how they impact protein function and phenotypic traits.

Null Alleles

A null allele is a variant of a gene that results in a complete loss of function of the gene product, often due to mutations that disrupt protein synthesis. This can occur through various mechanisms, such as frameshift mutations that lead to premature stop codons or deletions that remove essential coding regions. Identifying mutations that create null alleles is important for understanding genetic diseases and traits, such as skin pigmentation.

Impact of Frameshift Mutations

Frameshift mutations occur when nucleotides are inserted or deleted from the DNA sequence, causing a shift in the reading frame during translation. This often results in a completely different and nonfunctional protein, which can lead to a null allele. In the context of the zebrafish study, a frameshift mutation would likely create a transport protein that is unable to function, thereby affecting pigmentation.