Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: chris on 20/01/2012 08:34:53
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I was asked today by someone why some eggs are "double yolkers"; embryologically, I suspect that the gene programme that drives the development of the egg tissues plays out in two tissues side by side; these tissues are derived from some founder tissue that, rather like a monozygotic twin, spilts up earlier in the developmental pathway.
But I'd be interested in the insights and wisdom - and accurate answers - of others.
Chris
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The egg is essentially a single cell.
I was thinking it was like monozygotic twins. However, I believe the differentiation of the yolks comes prior to fertilization. Whereas in mammals, at least for monozygotic twins, the separation comes after fertilization.
I would be curious about a comparison of the genetic material between the yolks.
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The yolks are just a fat-rich energy store. The eggs we eat are unfertilised, as a rule, so the genetics argument ought not come into it - both yolk structures and related tissues should be genetically identical, I would think.
chris
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I was thinking it was like monozygotic twins.
It seems it's dizygotic twins ...
http://www.poultry.allotment.org.uk/Chicken_a/Chicken_Egg_Excess/double-yolk-eggs.php
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It seems it's dizygotic twins ...
http://www.poultry.allotment.org.uk/Chicken_a/Chicken_Egg_Excess/double-yolk-eggs.ph
That would make a lot of sense.
After meiosis, one would end up with haploid cells, which would be unlikely to divide again until fertilization.
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Thank you; that's very helpful. A double ovulation.