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Fig. 2. Targeting strategy to generate the Tbx2tm1Pa allele.
(A) Shown are the Tbx2 cDNA and the endogenous Tbx2 genomic
locus, where black indicates untranslated regions and gray represents the
T-box coding sequence. Two hundred and seven base pairs of exon 1 and all of
exon 2 were targeted for deletion with a construct containing a
neomycin-thymidine kinase selection cassette (neo-TK) flanked with
loxP sites and a negative selection diphtheria toxin element (DTA)
attached at the 5' end. A targeted line was electroporated in vitro with
a Cre recombinase gene to excise the selection cassette and generate
the final Tbx2tm1Pa allele with a
2.2 kb deletion.
(B) Southern blot analysis, with the 5' internal probe (5' int)
indicated in A, confirming the presence of the Tbx2tm1Pa
allele in genomic XhoI digests of yolk sac DNA. The wild-type
fragment is 5.1 kb, the mutant fragment is 2.8 kb. (C) PCR with the three
primers indicated in A amplifies a 180 bp wild-type product and an 88 bp
mutant product from yolk sac DNA. E, EcoRI; EV, EcoRV; N,
NotI; X, XhoI.