ekl1984

10+ Year Member
Nov 19, 2008
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Status
Dental Student
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

10+ Year Member
Jul 10, 2008
56
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Frankfort, NM
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Pre-Dental
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

10+ Year Member
Nov 19, 2008
10
0
Status
Dental Student
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

10+ Year Member
7+ Year Member
Jul 28, 2007
291
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Pre-Dental
They duplicate their chromatids prior to mitosis that occurs after fertilization.
 
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