In a one word response, mitosis.
In an explanation: Before the replication process, an ordinary sex cell contains only has 23 chromosomes. That is half the amount of a normal cell. So when the cells join together they make up the 46 pairs. Then through replication and division(i.e mitosis), the cells are copied to form in short a tiny human. You then forever live with the same amount of chromosomes in your normal cells.
Hello
Your bones moved in their sockets or bent just like your arm has a socket so does ur knee and legs and ankles and wrist and pretty much anything that has full rotation
Hope this helps
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What observations are you talking about