Recombinant DNA
Selective breeding can only shuffle the alleles a species already has. Genetic engineering removes that limit by taking a gene out of one organism and putting it into another.
Genetic engineering
Transferring a selected gene from one organism into the DNA of another, so that the second organism gains the characteristic that gene controls. The DNA that results, carrying material from two sources, is called recombinant DNA.
The steps in outline
- Identify the gene that controls the wanted characteristic, and locate it in the DNA of the organism that has it.
- Cut that length of DNA out, using enzymes that cut DNA at particular base sequences.
- Join it into the DNA of the receiving organism — often a bacterium — producing recombinant DNA.
- Let the receiving organism multiply. Every descendant carries the new gene and makes whatever it codes for.
Why the gene still works in a new organism
Because the genetic code is essentially the same in all living things. A gene is a sequence of the same four bases whether it sits in a human cell or a bacterial one, and a bacterium reads a human gene the same way a human cell does. That shared chemistry is what makes the whole technology possible.
This is what the last skill could not do
No amount of selective breeding could ever give a bacterium the gene for human insulin, because no bacterium anywhere has that allele to select. Genetic engineering crosses the boundary between species, which ordinary breeding cannot.
It is precise, and that is not the same as safe
Moving one known gene is a far more exact operation than crossing two whole organisms. But precision is about the method, not the consequences: what the new gene does in its new setting, and what happens if the modified organism spreads, still have to be tested rather than assumed.
A gene from one organism, working in another
Genetic engineering transfers a selected gene into another organism's DNA. The combined DNA is recombinant DNA, and it works because the genetic code is shared by all living things.