Fluorescent in Situ Hybridisation TEchniques Assignment

 

What is the difference between DNA and RNA that is critical for In Situ Hybridisation? 

 

DNA or Deoxyribonucleic acid is defined as the long polymer of nucleotides and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides. DNA is responsible for the genetic propagation of most inherited traits. On the other hand, PNA or Peptide Nucleic ps Acids are DNA mimics with a pseudopeptide backbone. The difference between the two molecules however is that PNA are stable under acidic conditions and resistant to nucleases as well as proteases compared to DNA. PNA oligomers can be shorter than oligonucleotides when used as hybridisation probes. Another advantage of PNA to DNA is that it permits the hybridisation of DNA samples under low or no salt conditions, since no interstrand repulsion, as occurs between two negatively charged DNA strands, needs to be counteracted. PNA shows a greater specifity of interaction to DNA or RNA than DNA or RNA itself. Furthermore, it also shows a stronger binding. Binding to DNA or RNA is essentially independent of salt concentration. Also, PNA is resistant to nucleases and proteases

What is the purpose of washing slides in the formamide solution after FISH?

Slides should be washed after a formamide solution. It is one of the causing factors in an effective FISH application. Not performing a post-hybridisation washing of slides may result in nonuniform cell permeability, variable target site accessibility, poor sensitivity, which are basically common disadvantages of the FISH process. Post hybridization washing is one of the methods that should be used to ensure FISH effectiveness.

Why is it necessary to incubate the “paint” probe with a highly repetitive fraction of the human DNA?

This is necessary because the paint probe without incubation can

 

 

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