Probe size

asanchez at asanchez at
Thu May 25 12:32:54 EST 2000

I will appreciate if somebody could help me with the following
question. I am a student working with trypsin mRNA. I am trying to
quantify its expression by northern hybridization, with a DNA probe. I
was planning to use a 25 nucleotides probe labeled with DIG, but today
a very good friend recommended me to use a larger probe. I have 100µg
of RNA, only 5µg must be messenger RNA, of which approximately 2µg must
be trypsin mRNA. If I use a 25 nt probe, the signal that I can get
could be weaker than the signal with a larger labeled probe???
For this kind of essays, what is the recommended size of the probe???
This trypsin mRNA has a length of 1200 nt approx., and they are very
conserved on the region 700-1200. Should I use a larger probe or with
the 25 nt probe is enough???

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