Biology · Rung 4 of 4

Genetic engineering

The first big application was insulin: in 1982 the human gene was put into a bacterium, and before that a tonne of pig pancreas gave little more than a hundred grams. An organism is transgenic when it carries a gene from another species; editing is a different thing, changing what was already there. CRISPR carries a guide that hunts a specific sequence and scissors that cut there, and the change slips in when the cell repairs the cut. What made it revolutionary is not being first but being cheap and aimable. And there is an ethical line science alone does not settle: editing a patient's cells affects whoever consented, while editing an embryo also changes their descendants, who cannot have a say. That is why almost every country allows the first and forbids the second.

Where this sits

Comes after
Gene expression

Exercises from this rung

Generated by the app, from easiest to hardest

  1. Where does injected insulin come from today?

    • From bacteria that were given the human gene
    • From a chemical synthesis out of minerals
    • From the pancreas of pigs and cattle
    • From human donors, like blood

    Why From modified bacteria, since 1982. Before that it was extracted from pig and cattle pancreas: a tonne of pancreas gave little more than a hundred grams, and many people were allergic to the small difference. Putting the human gene into a bacterium was genetic engineering's first big application and is still its most useful.

    easier

  2. What does a PCR do?

    • Reading a person's whole genome
    • Cutting a gene out and swapping in a different one
    • Destroying the virus's DNA inside the body
    • Copying one piece of DNA millions of times so it can be seen

    Why It copies one chosen piece of DNA over and over until there is enough to detect. Hence its power as a test: if the sample holds a single copy of the virus, PCR multiplies it until it shows. It cures nothing and changes nothing, it only amplifies, which is why it can come back positive on remnants that no longer infect.

    in between

  3. What does it mean for an organism to be transgenic?

    • That it carries a gene which came from another species
    • That a gene it had was removed
    • That its DNA was altered by radiation
    • That it was crossed with a wild variety

    Why That it carries a gene from another species, and that is the line between transgenic and edited: editing changes what was there, transferring brings something in. It is worth knowing that crossing varieties also moves thousands of genes blind and has been done for ten thousand years; what is new here is not touching the genome but touching it knowing where.

    harder