a. The Noxa1+ allele. b. The Noxa1neo-flox allele. c. The Noxa1flox allele. d. The Noxa1del1 allele. Fine horizontal lines, genomic DNA; numbered black rectangles, exons; labeled flags, oligonucleotide primers; green arrow, neomycin resistance cassette (Neo); blue triangles, loxP sites; yellow rectangles, FRT sites; labeled red lines, amplification products.