St Kilda Wren answered on 15 Nov 2017:
It’s possible to tweak things, yes, though this isn’t usually done in living animals. If scientists want to edit the genome, they have to do it before the zygote (that’s the fertilised egg, broadly speaking) starts to divide. Procedures such as this are strictly regulated, however, and scientists have to have a very(!) good reason for their experiment and stick to very(!!) strict rules governing research ethics. It’s not possible to change everything, though. The genome of an organism is very big, and extremely complex, and we don’t know what a lot of it does, nor what would happen if we changed a lot of things. Besides, if we change everything then we won’t have the same thing in front of us. Even small changes in the genome can have a big effect. Everything we and other living organisms are in terms of how we’re put together is based on our DNA. If we changed all the DNA of a St. Kilda wren, for example, what we’d end up with wouldn’t be a St. Kilda wren – it would be something entirely new and different.
Common Crane answered on 15 Nov 2017:
As St. Kilda Wren says, the strict regulations ruin everything. If not for this, me and my genetically engineered crane army would rule the world already 😛
Tomeu the snail answered on 16 Nov 2017:
It is not possible at the moment in snails, but it is something that we would like to do in the future – we would do this mainly so we can work out how genes work in snails, not because we want to create a “Franken-snail”. Of course, we would have to get ethical approval first (and find the money!).
Emperor Dragonfly answered on 17 Nov 2017:
Altering genes in insects is pretty straightforward, assuming that you can keep the insect in the lab!
The fruit fly (which is a genetic model organism – a well understood lab animal) has had many thousands of genes altered to try to find out what they each do, but we can grow thousands of flies at a time in the lab, and they reproduce every 14 days.
This would be a major hurdle for altering the genome of the Emperor Dragonfly as we can’t practically be grown in the lab, and it takes nearly a year for each generation. Then again why would want to alter us? – millions of year of evolution have made us practically perfect in everyway!
Lesser-Spotted Catshark answered on 17 Nov 2017:
Once you have a genome sequence, genome editing technologies such as crispr-cas9 can be used to specifically alter or replace almost any region of the genome. However, having a genome sequence is not a prerequisite for making transgenic organisms. Many earlier technologies still in use today insert new genes into organisms almost at random and they would still (usually) have the desired effect! Having a genome sequence does mean more types of changes are possible, with greater accuracy – thanks to newer genome editing technologies.
Another consideration is the timing of when these changes are made. As noted above, scientists often want to change the DNA of every cell in the organism to test its function. To do this, the DNA of the 1-cell fertilized zygote (sperm + egg) needs to be changed so that all of the descendant cells also have this change. If the changes are made later, ‘chimaeric’ or ‘mosaic’ animals result with a mix of changed and unchanged DNA. Today we can make these kinds of mosaics in sharks but we are still working on a method to make the changes to the zygote! This is difficult as sharks keep their eggs inside of them until quite late, and only produce 2-3 eggs at a time. Compared with some bony fishes which have external fertilisation and hundreds/thousands of eggs that makes the development of this technology in sharks a big scientific challenge.