Nomenclature: C57BL/6-Jak2^{tm1.1 Mrl}

• The targeting vector has been generated using C57BL/6J DNA and transfected into C57BL/6NTac ES cell line.
• Jak2 exon 3 contains the translation initiation codon.
• Exon 20 has been flanked by loxP sites.
• The conditional KO allele has been generated after Flp-mediated recombination by crossing chimeras to a Flp-Deleter on a C57BL/6 background.
• The conditional KO line has been subsequently backcrossed to C57BL/6NTac animals for at least 2 generations and the Flp-transgene was removed by segregation.
• The constitutive KO allele can be generated by Cre-mediated recombination.
• Deletion of exon 20 should result in loss of function of the Jak2 gene by generating a frameshift (premature stop codon in exon 21).
• The remaining recombination sites are located in intron regions of the genome.
• Data mining and Design performed in 2006.