发信人: leohawk (leohawk), 信区: Biology
标 题: Re: questions about DNA and hybridization,thanks a lot~
发信站: The unknown SPACE (Tue Apr 23 13:34:17 2002), 转信

【 在 lustre (紫色的花) 的大作中提到: 】
: You are really of great help and sound very professional:)
: I think I got the part about genome.My question about hybridization is:
: there are two RNA samples,one from for example tumor tissure,and the other is
: reference.
: Now,they are equally mixed and hybridized to the cDNA probes on the chip.As I
: understand,if they are all the complementary part of the cDNA,every one should
: base pair.but why at some spot,tumor RNA did more,which means the gene is
: expressed,does this means tumor RNA becomes more active?What about the less
: tumor RNA ones?Upregulated means some happened,does downregulated means the
: opposite happening?And what is the opposite?The gene shrinks?
: And what is the connection between mRNA and cDNA?
: Really appreciate your help and patience to my weird questions!

the central doctrin of genetics dictates

DNA-> RNA -> protein, though RNA -> DNA sometimes.

for the gene on DNA to work, they first has to be transcripted into RNA, then
in most cases, be translated into Protein. Upregulation means more
transcription of the gene into its corresponder mRNA... downregulation means
the opposite. Gene amplification and deletion happens but very rare, and, most
likely can't be detected by the method you are using.

Gene regulation, as you might have seen, can happen at many stages:

1. Pre-transcription (methlytion, amplification, deletion.......)
2. During transcription (initiation, enlongation, termination...)
3. Post transcription (mRNA splicing, exportation, mRAN decay...)
4. Pre-translation (mRNA stability, access to ribosome...)
5. During translation (binding to ribosome, initiation, elongation...)
6. Post translation (protein modification, exportation... degradation...)

what your method is capable is detecting the presence of certain mRNA, it
misses all the other parts. Fortunately, abundance of a genes mRNA, especially
when it can be compared with a good control sample, is indicative of how
well the gene is expressed.

hope it helps.


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