1. Fertilisation outcomes
Fertilisation outcomes (A) Fertilisation of a normal oocyte with a normal sperm cell leads to the formation of a diploid (2n) zygote. (B) If a nullisomic oocyte is fertilised, the resulting zygote will be monosomic for one chromosome. (C,D) Fertilisation of a disomic oocyte results in trisomic zygotes. Note that in (C), the oocyte has resulted from non-disjunction in meiosis I, and the resulting zygote contains one chromosome (ignoring crossover) from each maternal grandparent as well as the paternal contribution. In (D), the oocyte has resulted from non-disjunction in meiosis II, and the resulting zygote contains two chromosomes (aside from crossover regions) from one grandparent.
Maria Jackson et al. Essays Biochem. 2018;62:
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