My impression is that genetic information in eggs and sperm are consistent per individual. If so, what causes the combination of those two sources to vary so greatly? Some brothers or sisters are total opposites of each other despite the same “ingredients”. How does that happen genetically? Why would only one of a couples children inherit an expressive genetic disease? Etc.
In: Biology
Imagine your DNA is a bag of marbles, each marble has all sorts of unique colours.
When a sperm/egg is formed, it is made using half of the bag of marbles. This way when the 2 are combined you have a full bag of marbles.
When the time comes for a sperm/egg to be created, half of the marbles in your DNA are used to create it. There is no way to control which exact marbles are used, so each sperm/egg will have its own half-set of marbles.
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