Recombinant human insulin (made by inserting human DNA encoding insulin into E. coli) is one of the most widely used recombinant pharmaceutical products in the world. What segments of the human insulin gene are used to create recombinant bacteria that produce human insulin?

Verified step by step guidance

1. Understand the structure of the human insulin gene, which includes exons (coding regions) and introns (non-coding regions). The gene is initially transcribed as pre-mRNA containing both exons and introns.
2. Recognize that bacteria like E. coli cannot process introns because they lack the splicing machinery present in eukaryotic cells. Therefore, only the coding sequences without introns can be used to produce functional insulin in bacteria.
3. Identify that the mature mRNA of the insulin gene, which contains only the exons spliced together, is the correct template for producing recombinant insulin. This mRNA is reverse-transcribed to create complementary DNA (cDNA) that lacks introns.
4. Use the cDNA corresponding to the insulin gene's coding sequence to insert into a bacterial plasmid vector. This plasmid is then introduced into E. coli to enable the bacteria to produce human insulin protein.
5. Confirm that the inserted gene segment includes the sequences encoding both the A and B chains of insulin, which are the functional parts of the hormone, ensuring that the recombinant bacteria can synthesize the complete insulin molecule.

Key Concepts

Structure of the Human Insulin Gene

The human insulin gene contains coding regions called exons and non-coding regions called introns. The exons encode the insulin protein, while introns are removed during RNA processing. For recombinant production, only the coding sequences (exons) are used to ensure proper protein synthesis in bacteria.

Recombinant DNA Technology

Recombinant DNA technology involves inserting a gene of interest into a bacterial plasmid to produce a desired protein. In this case, the human insulin gene's coding sequence is inserted into E. coli, enabling the bacteria to express human insulin. This process requires isolating the correct gene segments and using vectors for gene transfer.

Expression of Eukaryotic Genes in Prokaryotes

Eukaryotic genes contain introns that bacteria cannot process, so only the intron-free coding sequences (cDNA) are used for expression in prokaryotes like E. coli. This ensures the bacteria produce functional insulin protein without errors caused by unprocessed introns.