Fig. 5.

Meiosis process analysis. Homologous chromosomes separate during the first meiosis and sister chromatids separate during the second meiosis (left). HFM1 participates crossover formation and complete synapsis of homologous chromosomes of the first meiosis and participates spindle assemble. The formation of poor-quality blastocyst missing one chromosome 21 may be due to the ovum missing one chromosome 21 from patient carrying HFM1 variation. This is due to abnormality in the spindle, thus causing a pair of homologous chromosomes 21 to shift to the same pole during the first division of meiosis. Primary oocytes lacking chromosome 21 undergo second meiosis to form an ovum missing chromosome 21 (right)