Final answer:
The term 'organism is Homo sapiens but the Expression System is Escherichia coli BL21 (DE3)' indicates that the protein originates from humans but is produced in E. coli bacteria using genetic engineering techniques.
Step-by-step explanation:
When an organism is Homo sapiens but the Expression System is Escherichia coli BL21 (DE3), it means that the protein is of human origin but produced in E. coli. This technique is part of genetic engineering where a human gene is inserted into the bacteria. The central dogma of molecular biology helps us understand this process, as it involves the transcription of DNA into RNA and the translation of RNA into a protein.
The recombinant protein production in E. coli is possible because all living organisms use DNA as their genetic material and share the same genetic code, allowing for the expression of human proteins in bacterial cells. In some cases, proteins require eukaryotic cells for proper post-translational modifications; therefore, yeast cells or transgenic animals may be used instead, since they are eukaryotes and can perform these modifications.