None of the other comments are really answering your question.
Normally, when a cell divides it duplicates it’s DNA so that each resulting cell has a full set of chromosomes. However the division that leads to sperm (and egg) cells is a different process. As others have stated, each resulting cell only have half the chromosomes. But, before the chromosomes split apart, they swap some DNA with each other. This allows the DNA to be mixed up a little, instead of just a clean half.
You have two copies of each autosomal chromosome. One from your father and one from your mother.
When a person produces sperm (or mature eggs) there’s a process called meiosis which separates one copy of each. It might be from your father, your mother, or they might mix and match in a process called recombination. This is different for each chromosome…
As you can imagine, this leads to tons of possible combinations of genetic material.
Because we have a HUGE amount of genes in our body, only half of which (less actually in some sperm cells or eggs) are put into each cell.
Long ago, evolution decided that a wide genetic difference in a species creates a higher chance of survival.
So, by mixing up genes, it ensures that SOME offspring will be better adapted in a changing environment, and some offspring won’t,allowing only genes needed for survival in the current situation are passed, but also allowing genes that aren’t currently useful, but may become useful someday, to also hang around.
Its like investing In a bunch of different stocks to ensure you don’t lose everything because of one problem
All cells in your body serve a specific purpose, sperm cells are just built to deliver your DNA to an egg. They have 1/2 of your DNA, split up because mixing up DNA is better in the long run, and they have a little tail that moves them forward (and probably some ways to sense what direction am egg is in). That’s all they need to be for the job they do.
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