hi, just doing some genetics study and hoping to get some help. when interference occurs chrosmosomal crossovers, interference causes the number actuall number off crossovers observed to occur LESS than expected. what does it mean if you observe MORE crossovers than statistically expected? is this also interference or soemthing else?

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By interference do you mean multiple cross-overs?

 

If so, then I don't think interference can produce more crossovers than expected, (unless you have a model which neglects triple crossovers or more i guess).

 

it may simply mean you have run across a 'hot spot' on a chromosome, where recombination is more likely. These are found by comparing chromosome maps from linkage mapping with chromosome maps from nucleotide sequencing. A suggested explanation is simply that hot spots contain many sites at which the meiotic endonuclease acts. The converse applies to 'cold spots' ofc.

 

I don't know of any other general principle that can produce extra cross-overs.