A number of criteria are applied when choosing the critical exon for a KOMP-CSD or EUCOMM allele, but not every gene can have all criteria fulfilled:

1) The critical exon(s) is selected so that its floxing (removal) by application of Cre produces a frameshift in *every* protein-coding transcript for the gene

2) The exon(s) is selected so that any residual transcript is subjected to NMD

3) The critical exon(s) is selected to be as 5-prime as possible, so that any residual protein product (if NMD doesn't occurr) is non-functional.

4) The insertion of the lacZ-neo trap requires that the 5' intron be large enough such that the trap can be placed without interfering with conserved / regulatory elements close to the splice sites. That is another constraint on the choice of critical exon(s)



Question:
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Hi,

I am a researcher and we have purchased CSD targeted knockout (with conditional potential) ES cells from you. I would like to know what is the basis for the selection of the "critical" exon before which the lacZ-neo genetrap is placed and which is then knockedout in the conditional. Could you please help me with that?

Appreciate your help,
Regards
Shachi Bhattt
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Answer:
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