Sexual life cycle.
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   Gametes  (sex  cells)  have 1 set (n) of chromosomes (haploid) and are
   produced by meiosis.
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   Somatic  (non-reproductive)  cells  have  2  sets  (2n) of chromosomes
   (diploid) and reproduce asexually by mitosis.
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   In humans, the haploid number is 23, and diploid number is 46.