What is a label moiety on gene probe?

Question

I'm a biology student and I'm now currently studying about gene probe. So there's this part where I read that shorter probe has a disadvantage where its not possible to put sufficient label moieties. What I dont understand here is, what is label moieties? What does it do and why do we need lots of label moieties on probes?

I've been searching online and really haven't found an answer. Thank you.

Answer 1

Jennifer,

 

Probe implies to a piece of DNA that is used to hunt for homologous sequence in genomic DNA. For instance, you clone a gene for s special transcription  factor from a worm (C. elegans).  Now you want to find out if this factor has a homologue in mice.  You take a piece of DNA from cDNA clone of worm, label it with p32 (radioisotope)  and use it as a probe on mouse genomic DNA to look for a homologous mouse gene/clone.

 

Shorter probe  ( a relatively short piece of DNA) has two disadvantages:

 

Firstly, it would hybridize in non-specific manner giving false positives.

 

Secondly, it would carry smaller number of p32 molecules(label) and therefore, signal would be low.

 

Hope it is clear, if not ask/post again, I shall explain.