19.1.2—Genetic engineering and gene expression

Genetic engineering deliberately modifies an organism by transferring genetic material so that a chosen characteristic can be produced. The transferred sequence becomes recombinant DNA in the host, but useful expression depends on the host being able to use the construct.

1. Identify the gene associated with the desired characteristic.
2. Isolate or obtain that gene as a suitable DNA sequence.
3. Cut the relevant DNA and the delivery construct, then insert and join the gene to form recombinant DNA.
4. Introduce the recombinant DNA into a host cell using a delivery system.
5. Select or identify cells that received the construct, then clone the successful cells when required.
6. Check that the transferred gene is expressed and that the intended product or characteristic is obtained.

The workflow has linked dependencies: the desired sequence must be obtained, the construct must be joined and delivered, and the host must recognise the regulatory information and express the gene. Enzymes, vectors, markers and promoters each support a later part of this chain; they are tools within the workflow, not interchangeable names for genetic engineering.

Do not treat transfer of DNA as proof of expression or a useful product. This card gives the whole engineering arc only. Restriction endonucleases, reverse transcriptase, DNA polymerase, ligase, vectors, promoters, markers, PCR, gel analysis, microarrays and bioinformatics are separate learning jobs; their detailed mechanisms belong to the matching cards.