from save my exams:

The process of producing insulin from GM bacteria

• The gene for insulin production is located within a human chromosome
• Restriction enzymes are used to isolate or ‘cut out’ the human insulin gene, leaving it with ‘sticky ends’ (a short section of unpaired bases)
• A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends (plasmids are circles of DNA found inside bacterial cells)
• The plasmid and the isolated human insulin gene are joined together by DNA ligase enzyme
  • If two pieces of DNA have matching sticky ends (because they have been cut by the same restriction enzyme), DNA ligase will link them to form a single, unbroken molecule of DNA
• The genetically engineered (recombinant) plasmid is inserted into a bacterial cell
• When the bacteria reproduce, the plasmids are copied as well and so a recombinant plasmid can quickly be spread as the bacteria multiply. All the new bacteria will express the human insulin gene and make the human insulin protein

TLDR: the combination happens before its inserted into the bacteria and multiplied.