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Updated: Aug 14, 2026

FISH for Pre-implantation Genetic Diagnosis
07:34

FISH for Pre-implantation Genetic Diagnosis

Published on: February 23, 2011

Meiotic outcomes in reciprocal translocation carriers ascertained in 3-day human embryos

Caroline Mackie Ogilvie1, Paul N Scriven

  • 1Guy's and St Thomas' Centre for Preimplantation Genetic Diagnosis, Cytogenetics Department, Guy's, King's and St Thomas' School of Medicine, London and Guy's and St Thomas' Hospital NHS Trust, London, UK. caroline.ogilvie@kcl.ac.uk

European Journal of Human Genetics : EJHG
|December 4, 2002
PubMed

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Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
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During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.
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Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
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