# semi identical twins? please explain

**URL:** https://boards.straightdope.com/t/semi-identical-twins-please-explain/397624
**Category:** Factual Questions
**Created:** [March 27, 2007, 12:43am UTC](https://boards.straightdope.com/t/semi-identical-twins-please-explain/397624 "2007-03-27T00:43:56Z")
**Posts on this page:** 1
**Page:** 2

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### Author: ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)
#### Post date: [March 28, 2007, 1:00am UTC](https://boards.straightdope.com/t/semi-identical-twins-please-explain/397624/21 "2007-03-28T01:00:42Z")

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> [@](#):
>
> The second, more likely scenario is that two sperm cells fused with a single egg, creating an embryo with three sets of chromosomes. Then, perhaps at the embryo’s two-cell stage, one cell would have shed the chromosomes from one sperm, and the other cell the other sperm’s genes.

This doesn’t make sense to me. How can a trlpoid cell have all those chromosomes line up at metaphase and have the right combination of chromosomes be pulled to the right end of the cells? It assumes the cell “knows” that two of one chromosome go one way and the other the opposite way.  
In mitosis, the chromsomes are spilt at the centromere and the number of chromosomes stays intact.

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