Thread: How are the effects of genes on the organism studied?

I know how RNAi works, where dsRNA is put into a creature then, because the dsRNA is cut up by the animal's cells (or rather, the animal's progeny's cells), it will bond to the mRNA the cell wants, effectively stopping the mRNA from being expressed and showing scientists what that gene does in the whole scheme of things. The dsRNA is put into the animal because a plasmid is inserted into bacteria with 2 promotors pointing in to DNA which is a tidbit of the DNA of the gene to be suppressed.

But I have only heard of this being used for nemotodes. How is the effect of a gene studied in, say, a mouse or any other animal which doesn't eat bacteria?

Thanks.

-Ajain

-by studying gene expression patterns.
-by studying protein product distribution of genes
-by using chemicals that effect certain genes.
-by using beads loaded with signalling molecules in tissue culture.
-by knocking out genes and creating transgenic mice with this construct
-by creating conditional knockout products in a transgenic mousline
-by creating hypomorph transgenic mouse lines.
-by creating hypermorph transgenic mouse lines.
-by creating ectopic expression constructs in transgenic mous lines.
-by computer modelling gene interactions.

I didn't mention all possibilities.

How is the effect of a gene studied in, say, a mouse

'knockout mice', as they're called, are very interesting.

Basically, the mice are genetically engineered to contain a gene encoding the enzyme Cre recombinase, an enzyme that recognises pairs of specific sequences on DNA called loxP sites and excises the DNA between them. The gene of interest is flanked with these loxP sequences, and a promotor region in front of the Cre recombinase gene is also included.

At a specific stage in the life cycle of the mouse, activator molecules specific for the Cre recombinase promoter region can be injected into the mouse. This causes the Cre recombinase gene to be translated. The Cre recombinase enzyme produced will then recognises the loxp sites on the mouse's genome, chop out the stretch of DNA between them and stick the loose ends back together. Now the gene of interest has effectively been removed from the genome and effects of this on the mouse can be studied.

This allows scientists to determine the function of particular genes, to see which genes are needed only in early development etc.

This kind of technology blows me away.

I looked up knockout mice (wikipedia) and the method they described involved making a very similar but still non-functional copy of the gene to be studied (plus a gene which is resistant to an antibiotic), then putting it in stem cells, exposing the cells to the antibiotic as a form of selection, then incorporating the ones that live into existing blastocycsts and putting those back into the mouse uterises...

Is there another method that, like you said Leukocyte, involves a messenging molecule and do you have any websites which might describe the method in detail?

Thanks

-Ajain

I tried looking it up on wikipedia before I posted and found the same thing as you. I just did a bit of quick research and what I'm talking about is generally referred to as tissue-specific knockout mice.

It looks like the general process is to use a promoter region for the Cre recombinase gene that is only used in one specific cell type, so that the gene will be knocked out in that cell type only (hence tissue-specific). I can't find too much information on injecting an activator to initiate the knockout, but the links below briefly touch on systems that involve administering drugs like tetracycline (through diet) to activate the gene so I may have been thinking of that instead.

Try these anyway, I just googled 'tissue-specific knockout mice'.

http://www.scq.ubc.ca/?p=287
http://jaxmice.jax.org/library/notes/501c.html

Maybe the question should be "How are the effects of the organism on the genes studied?"

Genes are just tools that the body uses:

http://www.biotech-info.net/moms_diet.html

Some of the mothers consumed supplements high in very simple molecular compounds that zip around the genome turning off genes. One silenced gene was for yellow fur; when it is turned off, the mouse's fur color defaults to brown. For the mice, it wasn't just that "you are what you eat," but that you are what your mother ate, too.


Biologists have long known that having a particular gene is no guarantee you will express the associated trait, any more than having a collection of CDs will fill your home with music. Like CDs, genes are silent unless they are activated. Because activating and silencing doesn't alter the sequence of the gene, such changes are called epigenetic.

http://www.harvardmagazine.com/on-line/0103109.html

Maybe the question should be "How are the effects of the organism on the genes studied?"

I think if he wanted to know the answer to that, he would've asked.

This thread is not about epigenetics lackadaisal. I know you think that epigenetics is some amazing new discovery that blows the theory of evolution out of the water, but it's not. You need to educate yourself a bit more.

I just found mention of a nother method on a site studying apoptosis of rods and cones in Xenopus frogs. It was described as "making the sperm swell, then adding DNA." Therefore the fertilized eggs wouldn't need to be split into stem cells, reinjected, etc...

The site is here: http://www.uchc.edu/dsp/trans.html

--Ajain

EDIT: Found a procedure that explains it in detail...
http://www.xenbase.org/genetics/tran...gen-intro.html