How to "normalize"

[DREDD]

MELANSOND wrote:
> 
> About a year ago I was under the impression that one could use the actin gene
> as a standard for Northerns. However, it appears that actin is not expressed in
> all tissues at all times at the same levels, so that there may be variations
> across your lanes using this standard, which makes it hard to normalize.
> Fortunately, I was recently informed that one could use a probe for the
> ribosomal RNA to better provide accurate standards.  None of this may answer
> your question. I had thought that the only use for these "standards" was to
> provide a control for the loading amounts in the lanes.
> Hope this helps

You are right in all accounts.  But the standard can be used for more than loading.  For 
instance, if you want to check the effect of a particular stimuli on transcription of gene 
X.  You can measure the levels of X and compare the ratios of X to your standard 
gene.  One MUST be sure that the treatment does not affect the expression of the 
standard gene.

There are many genes that can be used as a standard which one you pick depends on 
what effect the treatment will have on it:  beta actin, gamma actin, cyclophilin, G6PD,
MLC-2, 28s or 18s ribosomal are some of the choices.