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Old 05-09-2011
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DNA Transgenic mouse and gene insertion in fertilized eggs versus stem cells?

Transgenic mouse can be produced by introducing cloned gene either to fertilized ova or to stem cells. What I do not understand is why the former method does not allow expression of recessive traits, whereas the latter method does.

Pls advise
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Old 05-10-2011
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Anybody has insight on this? USMLE forums staff?
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Old 05-10-2011
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Default This my understanding

In the case of the ova, they don't use homologous recombination. The inserted gene exists with original genes, the original genes are not deleted. Therefore, in case of a recessive disorder it might not get expressed (because you need two copies of the gene to be expressed).

In the case of stem cells, they use homologous recombination, this means that the inserted gene will replace the existing gene and will be available in two copies and therefore recessive disorders can be expressed.
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Old 05-10-2011
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Hey,

So I did some research on google and went over the KLN but couldn't find much on your question. But heres what I think might be the answer-

When you introduce a cloned gene into an embryonic stem cell, the homologous recombination can be used to replace the existing copies of the gene with the cloned gene. This allows dominant AND recessive alleles to be studied.

When you introduce a cloned gene into a fertilized ova, the offspring resulting from this will contain the transgene in ALL of their cells, including the germline. These genes are very rarely expressed as they do not incorporate into the nuclear DNA. This method is more useful for studying Dominant effects.

Sorry, its still not very clear to me either but I would like to know the answer as well!
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Old 02-20-2013
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Default Kindly dispel my confusion.

Why can't we perform recombination in the fertilized ova of mice and achieve the same results as with homologous recombination of embryonic stem cells?

Afaik, Kaplan says that we need to 'microinject' a cloned gene into a fertilized ovum. Does this mean that the fertilized ovum is currently nascent and not dividing and hence is inaccessible by the gene delivery vectors (coz we need cells to be dividing in order to be infected and manipulated by retroviruses), while the embryonic stem cells are dividing and can be manipulated by recombination?

I feel I need a university course in genetics
But on a serious note, do I look like in need of another reference along with KLN?? HY Cell and Molecular Biology / Lippincott?
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