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bio question

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ekl1984

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So I know that an egg cell and a sperm cell are each haploid (with 23 chromosomes and 23 chromatids). Then when they fuze they create a diploid zygote with 46 chromosomes. But when are the chromatids of each chromosome duplicated?
 

911dds

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Once the sperm and egg meet they continue with meiosis II. Remember the egg stopped at Prophase I of meiosis. Ovulation completed Meiosis I and once the egg and sperm join it continues with Meiosis II the duplication portion. Am I correct? Anyone?
 

ekl1984

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I think you have things confused. There is no "duplication portion" in meiosis II. When the egg and sperm fuze they have each gone through meiosis II and are haploid with 1 chromatid on each chromosome. The zygote is diploid, but i think each chromosome still had only 1 chromatid. so my question is, when do the chromosomes duplicate their chromatids?
 

chessxwizard

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They duplicate their chromatids prior to mitosis that occurs after fertilization.
 
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