system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 - Can seedless fruit plants only be grown by propagation?

How do you continue to grow fruit that has been modified to no longer contain seeds, such as seedless grapes?

I understand you could maybe propogate from existing plants but without seeds it could seemingly never be planted from a seed?
gpt
The seedless characteristic isn’t always *genetic*... well not exactly. It doesn’t evolve over time and get passed through generations, it pops up so the offspring of a plant with seeds is a plant without seeds. Plants are supposed to have 2 sets of chromosomes so they can pass on exactly half their DNA (which is exactly 1 set) to the next generation. The other parent provides 1 more set of chromosomes, and the other half of the DNA the child will inherit. Not too different from humans. Unlike humans, plants can survive with 3 sets of chromosomes and the only problem they have is inability to reproduce (no seeds).

If you can find or make another “defective” seed with 3 sets of chromosomes, you can make another seedless plant from a plant with seeds. This is where they came from in the first place.

In practice, yes, they are usually propagated, and this is can be an issue. Bananas are all so similar to each other that massive amounts of bananas are frequently wiped out by one disease they are all equally vulnerable to.