If an apple tree fertilizes another tree of the exact same kind, why will the seed of one tree produce different tasting apples?
In: Biology
Allow me to use a metaphor, or is it an analogy, here…if a man fertilizes two different women in the same family, for example, sisters, why will he produce children that look different? It’s that sort of concept, I think
Background: Genes usually come in more than one form. The classic example (though somewhat inaccurate as we know now) is eye color. Blue and Brown. Brown is dominant and will show if the person has two copies of brown BB or one of each brown and blue Bb. Blue eyes are bb. Sometimes genes are not dominant or recessive. Think of a plant with a red and a white gene making a pink flower.
Back to the apple trees. Unless all the genes the twins (^^Ed or self fertile single tree) possess are all the exact same copy for every gene, the babies will end up with mixes that are not the same as the parents. If the parents are AA, bb, CC, dd for ALL genes, the kids would turn out the same. But the parents are more likely AA, Bb, Cc, DD or similar thus the kids could end up with BB or bb and CC or cc which the parents were not.
Funny that you used apples as your example! It is actually very difficult to get good tasting apples through natural fertilisation, as every tree will have different tasting apples, the only way to get consistently good apple trees is through grafting.
So yes, even if you plant the seeds of a single apple, every plant will have different apples, genetics are weird and random. If a pair of identical twins would have children with another pair of identical twins, their children would not be the same.
Because the two trees have different genetics and the apple seed will contain information from both. Just like you are not a clone of your father, you are a mix of him and your mother, the new Apple will be unique. Unfortunately for apples this normally means they don’t taste very good.
In the process of creating sex cells (sperm, egg cells, pollen, …) the genes of each chromosome pair get randomly reshuffled, creating a unique DNA sequence.
It’s the same reason why you don’t look like your siblings (unless you’re an identical twin).
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