There are 8,324,608 possible combinations of 23 chromosome pairs. As a result, two gametes virtually never have exactly the same combination of chromosomes. Each chromosome contains dozens to thousands of different genes.
Epididymis
Tube in each part of the testis where sperm is stored temporarily
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non-disjunction is a pathological event that occurs during the second anaphase in meiosis when sister chromatids are not separated. As a result one of the resulting cells will have 1 extra chromosome and the other will be 1 short. An example of a non-disjunction that can occur in humans is Down syndrome that has a frequency of about 1/1000 people. It is caused by the non-disjunction of the 21st pair of chromosomes.
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