Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.
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Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr
Mutant 1: Met-Trp
Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr
Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-His                                  _

Use this information to answer the following questions:

Another mutation (mutant 4) is isolated. Its amino acid sequence is unchanged from wild type, but the mutant cells produce abnormally low amounts of the wild-type proteins. As specifically as you can, predict where this mutation exists in the gene.

Key Concepts

Gene Structure and Function

Genes are segments of DNA that encode proteins, consisting of exons (coding regions) and introns (non-coding regions). The sequence of nucleotides in a gene determines the amino acid sequence of the corresponding protein. Mutations can occur in various parts of the gene, affecting protein production and function. Understanding the structure of genes is crucial for predicting the effects of mutations.

Types of Mutations

Mutations can be classified into several types, including point mutations, insertions, deletions, and frameshift mutations. Each type can have different effects on protein synthesis. For instance, a mutation in a regulatory region may lead to decreased protein expression without altering the amino acid sequence. Recognizing the type of mutation helps in predicting its impact on gene function.

Transcription and Translation Regulation

The processes of transcription (DNA to RNA) and translation (RNA to protein) are tightly regulated. Mutations can affect regulatory elements such as promoters or enhancers, leading to changes in the amount of protein produced. In the case of mutant 4, the unchanged amino acid sequence suggests a mutation in a regulatory region that affects transcription levels, resulting in lower protein production despite normal coding sequences.