how is this possible?

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bobs
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how is this possible?

Post by bobs » Wed Dec 20, 2006 9:12 pm

Every cell in the body has a full complement of all genes, however each cell type reads only certain genes. For example, both white blood cells and liver cells have genes for making digestive enzymes but they do not read them.

How in the world is this possible??

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LilKim
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Post by LilKim » Wed Dec 20, 2006 9:59 pm

So DNA is modified by other proteins/molecules such as Methlyation, Acetylation, Phosphorylation, Ubiquitination and Sumylation.

These groups and other specific protiens (for example HP1) attach to DNA-itself and/or histone protiens (DNA wraps itself around histone proteins). These molecules function like traffic signs... Like Red Lights or green lights.. that tell polymerases if the should transcribe genes 'marked' by these "traffic-signs".

So essentially what happens is these molecules differentially decorate the promoter (regulatory regions) of genes in different tissues. Therefore certain genes expressed by pancreatic cells wil not be expressed by liver cells.. and vice versa based on the "traffic signs".

.... of course this is an oversimplified explanation because gene/regulation can also be controlled at the translational level by siRNA/miRNA .... (but this is probably way beyond the scope of your question)

Anyways, please let me know if you need furhter clarification or additional explanations!

Take care!
- KIM

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Mjhavok
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Post by Mjhavok » Thu Dec 21, 2006 1:29 am

The receive signals that make them differentiate.

Also note that not all cells have a full complement of genes. Red blood cells have no nucleus and gametes (sperm and egg) only have half the complement.
Forgive him, for he believes that the customs of his tribe are the laws of nature!

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sachin
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Post by sachin » Sun Dec 24, 2006 4:50 pm

Go google and seach for Eukaryoti transcriptin,
Mediators,
Promoters.

Your answer is behind these keywords.
Senior Education Officer, BNHS, India. www.bnhs.org

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Reason lies in two words "Me and Mine".

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fluktuacia
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Post by fluktuacia » Sun Dec 24, 2006 9:09 pm

well.. how than these specific proteins know which gene should be expressed in which cell.. how they know that in the case of liver cell they should turn off different genes than in the cheek cells? who tell them:)

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sachin
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Post by sachin » Mon Dec 25, 2006 8:23 am

fluktuacia wrote:well.. how than these specific proteins know which gene should be expressed in which cell.. how they know that in the case of liver cell they should turn off different genes than in the cheek cells? who tell them:)


Go google and seach for Eukaryoti transcriptin,
Mediators,
Promoters.

Your answer is behind these keywords.


Same for you too.. :P

Mediators .... :o
Senior Education Officer, BNHS, India. www.bnhs.org

Bitter Truth!
Who says reason for world war III will be Petrol?
Reason lies in two words "Me and Mine".

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