If I have two fluorescent probes for sections of DNA (FISH), what is the shortest distance that I can detect with those probes? How many kb do they need to be away from each other in order to show up as separate probes?
Hi. It depends on a resolution and two probes you can see as separate probes when a distance is 1 000 000 bp. When this distance is less than a given value, you can see a middle colour - it means a colocalization to some extend; thus, you are not able to separate them and only one colour is present (the middle colour). Based on the resolution of mapped sequences, you can use: (i) extended DNA fibers (EDFs) to increase the resolution of these sequences - you can physically map 1 000 kb, (ii) flow sorted chromosomes or pachytene chromosomes - at least 10 000-100 000 and more bp to check how these probes work. In case of questions, do not hesitate to contact me. Best wishes. Tomasz
Hi Kim,
In a recent study from the Bickmore lab, you will find that, using a variety of fosmid probes of adjacent loci, it is possible to visualize by FISH very short intervals (down to 100kb).
See Eskeland et al 2010 (Mol Cell): http://dx.doi.org/10.1016/j.molcel.2010.02.032
Best,
Pierre
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