The following figure contains several examples of the Shine–Dalgarno sequence. Using the seven Shine–Dalgarno sequences from E. coli, determine the consensus sequence and describe its location relative to the start codon.

검증된 단계별 안내

Step 1: Understand the Shine–Dalgarno sequence as a ribosomal binding site in prokaryotic mRNA, typically located upstream of the start codon, which helps initiate translation by aligning the ribosome with the start codon.

Step 2: Collect the seven Shine–Dalgarno sequences from the given E. coli examples and align them to identify conserved nucleotides across all sequences.

Step 3: For each position in the aligned sequences, determine the most frequently occurring nucleotide to establish the consensus sequence. This can be done by creating a position weight matrix or simply noting the dominant base at each position.

Step 4: Note the typical location of the Shine–Dalgarno sequence relative to the start codon, which is usually about 5 to 10 nucleotides upstream (5' direction) of the AUG start codon.

Step 5: Summarize the consensus sequence and describe its position relative to the start codon, emphasizing its role in facilitating ribosome binding and translation initiation.

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주요 개념

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Shine–Dalgarno Sequence

The Shine–Dalgarno sequence is a short, conserved ribosomal binding site in bacterial mRNA, typically located upstream of the start codon. It helps recruit the ribosome to initiate translation by base-pairing with a complementary sequence in the 16S rRNA of the small ribosomal subunit.

Consensus Sequence

A consensus sequence represents the most common nucleotides found at each position in a set of similar sequences. It summarizes conserved features and is used to identify functional motifs, such as the Shine–Dalgarno sequence, by highlighting the typical nucleotide pattern.

Relative Position to the Start Codon

The Shine–Dalgarno sequence is located a few nucleotides upstream (usually 5-10 bases) of the start codon (AUG). This precise positioning is critical for proper alignment of the ribosome with the start codon to ensure accurate initiation of protein synthesis.