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.

Write out the mRNA sequences encoded by each template strand, and underline the start codons.

Key Concepts

DNA and RNA Transcription

DNA transcription is the process by which a segment of DNA is copied into mRNA by the enzyme RNA polymerase. During this process, the DNA template strand is read, and complementary RNA nucleotides are assembled to form a single-stranded mRNA molecule. Understanding this process is crucial for determining the mRNA sequence from a given DNA template.

Codons and Start Codon

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or signal the termination of protein synthesis. The start codon, typically AUG, signals the beginning of translation and is essential for the correct initiation of protein synthesis. Identifying the start codon is vital for accurately translating the mRNA into a protein.

Mutations and Their Effects

Mutations are changes in the DNA sequence that can affect the structure and function of proteins. They can be classified as silent, missense, or nonsense mutations, depending on their impact on the resulting protein. Understanding how mutations can alter codons and potentially affect the start codon is important for analyzing the differences between wild-type and mutant sequences.