Table 1 Chromosomal mosaicism in presumably normal human tissues.

Ovarian tissues

Small, but significant proportion of aneuploid cells (trisomy 21) in ovarian tissues of normal female fetuses

[15]

15–20% of human oocytes

[19]

Sperm

2–10% of spermatozoa (0.1–0.2% per chromosome)

[20]

Chorionic villi

approaching 24% (~1% of aneuploid cells per chromosome)

[13]

Fetal human brain

approaching 30% (~1.5 of aneuploid cells per chromosome) 35% including chromosomal mosaicism confined to the fetal brain

[3, 13]

Placenta

No generalized data; chromosomal mosaicism observed in ~2% of foetuses (9–11 weeks of gestation) referred to prenatal diagnosis

[21]

Skin (adults)

2,2% and 4,4% (in young and old individuals, respectively)

[22]

Liver (adults)

~3%

[23]

Blood (adults)

1–2% (randomly selected autosomes) and 3% (chromosome X)

[24]

Adult human brain

0.1–0.7% (autosomes and chromosome Y), 2% (chromosome X); tending to approach 10%, in total

[3, 4, 6]