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Name: Marv J Mikesh
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Question:
How do homologous chromosome pairs cross-over during prophase I of meiosis?



Replies:
As the chromosomes begin to prepare for meiosis, they go through duplication, just as in mitosis. Except, during prophase I, all 4 strands of one homologous pair segregate together. These four strands are "stuck together" like four pieces of spaghetti. This is called synapsis, and the four strands together are called a tetrad. In this "twisted" condition, it is possible for adjacent strands to break and exchange homologous segments - this is crossing over. Is this detailed enough, or do you need more?

Ellen



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