• Question: Is the entire yolk of an egg the nucleus, or is it just part of it?

    Asked by blytheacres to Judith on 19 Jun 2012.
    • Photo: Judith Sleeman

      Judith Sleeman answered on 19 Jun 2012:

      The yolk of an egg isn’t the nucleus at all: did I confuse you with my cell/fried egg comparison on my profile? Sorry.

      The yolk of a bird’s egg is there to provide food for the growing chick. The fertilized ‘oocyte’, with it’s nucleus inside, that will grow to be the chick is there in the egg but it can’t be seen with the naked eye. It’s too small.

      Human cells growing in a dish look a bit like fried eggs with a big oval ‘blob’ in the middle (the nucleus) and a big ‘splat’ of cytoplasm around it. But they’re MUCH smaller: only about 2/100ths of a millimetre across. I’ll try and post a picture on my profile for you.

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