Method for producing vector in which foreign gene has been introduced

A method of producing a vector, in which a foreign gene has been introduced between said adjacent sequences C and D, comprising the steps of:

• (1) preparing a vector comprising a replication origin, sequence A, marker gene X, sequences C and D for introducing a foreign gene by homologous recombination, and sequence B that is homologous with said sequence A, in that order, wherein said sequences C and D are directly or indirectly adjacent, and for use in introducing the foreign gene between said adjacent sequences C and D;
• (2) preparing a nucleic acid fragment containing sequence C′ that is homologous with said sequence C, a foreign gene, and sequence D′ that is homologous with said sequence D, in that order;
• (3) by exposing said vector and said nucleic acid fragment to conditions to cause homologous recombination, generating a vector in which the foreign gene has been introduced between said adjacent sequences C and D, and forming a host that may contain the vector in which the foreign gene has been introduced between said adjacent sequences C and D;
• (4) culturing the host obtained in Step (3), and selecting, from the culture, a host containing the vector in which the foreign gene has been introduced between said adjacent sequences C and D by identifying the expression of marker gene X as an indicator;
• and
• (5) extracting from the host selected in Step (4) the vector in which the foreign gene has been introduced between said adjacent sequences C and D.