Down syndrome results from trisomy of chromosome 21. Which of the following is not an example of how this may have happened?

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Quizplus · Accepted Answer

Inversion of a portion of chromosome 21 during S phase is not a way in which Down syndrome can occur. Down syndrome is caused by either an extra copy of chromosome 21 or a partial or complete extra copy of the chromosome due to non-disjunction during meiosis. Translocation of chromosome 21, failure of the homologous pair for chromosome 21 to separate in meiosis I, and failure of the sister chromatids in a duplicated chromosome 21 to separate in meiosis II are all possible ways in which Down syndrome can occur.

Down Syndrome Results from Trisomy of Chromosome 21