The two gels illustrated contain dideoxynucleotide DNA-sequencing information for a wild-type segment and mutant segment of DNA corresponding to the N-terminal end of a protein. The start codon and the next five codons are sequenced.

What is the cause of the mutation?

Verified step by step guidance

1. Examine the DNA sequencing gels for both the wild-type and mutant segments. Identify the nucleotide sequence for each segment by reading the bands from bottom to top (5' to 3' direction).
2. Compare the nucleotide sequences of the wild-type and mutant DNA segments. Look for differences in the sequence, such as substitutions, deletions, or insertions.
3. Translate the nucleotide sequences into their corresponding amino acid sequences using the genetic code table. Start at the start codon (AUG) and proceed codon by codon.
4. Determine how the mutation affects the amino acid sequence. Check if the mutation causes a missense mutation (change in one amino acid), nonsense mutation (premature stop codon), or frameshift mutation (alteration of the reading frame).
5. Conclude the cause of the mutation based on the observed changes in the DNA and protein sequences. For example, if a nucleotide substitution leads to a different amino acid, the mutation is likely a point mutation causing a missense effect.

Key Concepts

Dideoxynucleotide Sequencing

Dideoxynucleotide sequencing, also known as Sanger sequencing, is a method used to determine the nucleotide sequence of DNA. It involves incorporating dideoxynucleotides, which terminate DNA strand elongation, allowing for the identification of the sequence based on the lengths of the resulting fragments. This technique is crucial for analyzing mutations by comparing the sequences of wild-type and mutant DNA.

Codons and Start Codon

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. The start codon, typically AUG, signals the beginning of translation and is essential for proper protein formation. Mutations affecting the start codon or subsequent codons can lead to changes in the amino acid sequence, potentially altering protein function.

Types of Mutations

Mutations can be classified into several types, including point mutations, insertions, deletions, and frameshift mutations. Point mutations involve a change in a single nucleotide, which can lead to a different amino acid being incorporated into a protein. Understanding the type of mutation present in the DNA sequence is critical for determining its potential impact on protein function and the underlying cause of the mutation.