Trisomy and 47 somatic cells ... ? - QVault

[Dental24/7]

Qvault says that someone with trisomy, specially down syndrome has 47 somatic cells. But, somatic cells are cell that are NOT sex cells. So 46 (normal) - 2 (sex cells) + 1 extra somatic cell is = 45. They are saying 47. What am I missing here? I got this question wrong. I am getting 35/40, but these certain questions are keeping me from getting the additional 5 or so ... any insight?

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[Alpha Centauri]

Qvault says that someone with trisomy, specially down syndrome has 47 somatic cells. But, somatic cells are cell that are NOT sex cells. So 46 (normal) - 2 (sex cells) + 1 extra somatic cell is = 45. They are saying 47. What am I missing here? I got this question wrong. I am getting 35/40, but these certain questions are keeping me from getting the additional 5 or so ... any insight?

You are overthinking it. Trisomy 21 just means there is a 3rd copy of chromosome 21 inside of the genome. This was present at conception, so all your cells would have this same defect. (I am pretty sure at least) .This means that you normally should have 2 copies of chromosome 21, and for all other chromosomes of course. Since you have trisomy of only 1 chromosome, you have 46+ 1 extra = 47!