縱使極體染色體異常仍有95%胚胎染色體正常

最常見的胚胎分裂異常為PSSC (premature sepatation of suster chromatin)
可由極體(polar body)分析間接老瞭解胚葉細胞之染色體狀況
縱使極體染色體異常,仍有相當高比例(95%)胚胎染色體呈現正常，顯示胚胎分裂過程自我修復異常鑲嵌胚葉細胞之功能

http://humrep.oxfordjournals.org/content/early/2012/11/20/humrep.des393.long

Figure 1

(A) Normal segregation (N) of homologous chromosome to first polar body (PB1) in meiosis I and then segregation of separated sister chromatids to second polar body (PB2). (B) In non-disjunction, there is a loss (L) of genetic material in PB1 with a reciprocal gain (G) in PB2, resulting in an unbalanced, trisomic zygote (G). (C) Although PSSC also results in a loss (L) in PB1 and gain (G) in PB2, the meiosis I error is compensated and results in a balanced, euploid zygote (N) after fertilization.