Which DNA segment is not required specifically for an expression vector (for use in E. coli) ?

a. origin of replication

b. operator

c. ribosome binding site

d. promoter

e. transcription termination sequence

b. operator

Explanation:

An expression vector is usually a plasmid or a virus designed for gene expression in cells, it's designed to act as an enhancer and promoter to efficient transcription of the gene that it carries, meaning it is used for protein production.

As any other vector expression vector may have an origin of replication, a selectable marker, and multiple cloning sites, it also needs elements that are necessary for gene expression, a promoter, a ribosomal binding site, and a start, terminal codon and a transcription termination sequence.

An operator contains the code to begin the process of transcribing the DNA message of one or more structural genes into mRNA, it works as a repressor to regulate the gene expression, since the function of an expression vector is the protein production an operator is not specifically required.

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