6 Questions
What is the role of the promoter in E. coli gene expression?
Recognized by the Sigma subunit of RNA polymerase
Where is the initiation codon of a gene typically located in relation to the ribosome binding site?
Immediately downstream of it
What is the terminator responsible for in gene expression?
Marking the end of the gene for transcription termination
Why is it unlikely that a significant amount of recombinant protein will be synthesized in E. coli if a foreign gene is simply ligated into a standard vector?
The absence of proper expression signals for E. coli
Which component of the transcriptional and translational apparatus recognizes the ribosome binding site?
Ribosome
How does the terminator signal the end of gene transcription?
By forming stem-loop structure
Study Notes
Cloning Foreign Genes in E. coli
- Cloning a foreign gene in E. coli without additional signals is unlikely to produce significant amounts of recombinant protein.
- The expression of a cloned gene in E. coli requires specific signals recognized by the bacterium for transcription and translation.
Signals Required for Gene Expression
- Promoter: a short sequence of nucleotides that indicates the starting point of transcription, recognized by the Sigma (σ) subunit of RNA polymerase.
- Ribosome binding site: a short nucleotide sequence recognized by the ribosome as the point of attachment to the mRNA molecule, located upstream of the initiation codon.
- Terminator: a nucleotide sequence that marks the end of the gene, forming a stem–loop structure through self-base pairing, signaling the termination of transcription.
Learn why simply ligating a foreign gene into a standard vector and cloning it in E. coli may not lead to significant production of recombinant protein. Discover the importance of signals recognized by the bacterium for gene expression.
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