If you try to grow an apple tree from an apple seed, there is a nearly 100% guarantee that the apples will be COMPLETELY different from the one that had the seed.
Planting apple seeds does not mean you’re going to get what you want. You might still get an apple tree, but it almost certainly won’t be the kind of apple tree from which the seed came from.
This is because seedling apples are an example of what’s called “extreme heterozygotes,” meaning that rather than inheriting DNA from their parents to create a new apple with those characteristics, they are instead significantly different from their parents.
Of course, there are apple orchards that contain only one type of apple tree, so there must be a way to get the kind of tree that you want. This is true, and it’s done through a process called grafting.
Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together.
Another way to think of this is the root providing the scaffolding for the plant, while the other plant’s characteristics are put on top of that to make the kind of tree you want.
Grafting allows growers to choose pretty exact characteristics for their trees. The rootstock used for the bottom of the graft can be selected to produce trees of a large variety of sizes, as well as changing the winter hardiness, insect and disease resistance, and soil preference of the resulting tree.