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1answer
25 views

When do 3 germ layers form in embryo? And why is there only one mature egg formed?

During the process of pregnancy, when do the 3 germ layers form in embryo? Is it after formation of gastrula? Also, during oogenesis, why does only one mature egg form? Why don't use polar body egg ...
1
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1answer
66 views

How do harsh conditions cause an increase in the male birth ratio?

I've heard that in harsh conditions more human baby boys are born than girls because a bigger ratio of them will die before reproductive age. But in which aspects of the random gene combination while ...
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3answers
2k views

When is the second polar body extruded from the egg nucleus?

When does the second polar body gets expelled from the egg nucleus during oogenesis ? I know that it occurs after the entry of the sperm into the secondary oocyte but does it occur before the ...
2
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1answer
92 views

How does the genetic material differ between dizygotic twins and ordinary siblings?

I am going to give a rough presentation on twin studies. The terms heritability and concordance are included already, but I struggle with understanding the difference of the genetic material of ...
4
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2answers
2k views

Is secondary follicle or Graafian follicle arrested in the second metaphase of oogenesis?

My note about which I am not sure: Secondary oocyte is arrested in the metaphase II monthly after puberty until fertilization with sperm. The following picture also satisfies my sentence: . So ...
3
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1answer
296 views

How do you see the stage of the second meiotic arrest in oogenesis in the given video?

My old question raised this new question. After reading this page I can say now that metaphase is the stage in which the second meiotic arrest occurs within oogenesis: The oocyte is arrested again ...
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2answers
17k views

At what stage of meiosis does “first meiotic arrest of oogenesis” occur?

An exam question asked what stage of meiosis corresponds with "first meiotic arrest of oogenesis". I can't work out the answer from the wiki page - can anyone explain which step this refers to?