• protist@mander.xyz
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    5 days ago

    TIL

    • In the majority of cases, the extra copy of chromosome 21 comes from the mother through the egg.
    • In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
    • In the remaining cases, the error occurs after fertilization, as the embryo grows.