p53-/-,如果是老鼠的话，就是p53敲除的纯合子，如果是细胞的话就是这种细胞敲出了这种基因的，一般细胞水平上的话可能会用到条件性敲除，利用cre/loxp系统，个体水平上的话一般用传统的基因重组的原理，条件性敲除用的也挺多的，一般都是公司做。还有一些包括诱导性敲除，比如四环素诱导的基因敲出，你可以在网上查一下这些基因敲出的原理，我懂得也不多，呵呵，我这边有一些这方面的课件，如果你想要可以传给你的。

这个细胞的式这么得到的
The targeting vectors used in this experiment were constructed so that the first codons of the drug resistance markers replaced the first codon of the p53 gene within exon 2. Transfection was done with LipofectAmine (Life Technologies) and subconfluent monolayers of cells. The LipofectAmine-DNA mixture was removed 3 hours after transfection and cells were grown in complete medium for 18 hours before they were replated in selective medium. After transfection with the neomycin-resistance vector, resistant colonies were grown in the presence of geneticin (0.4 mg/ml) (Gibco). One geneticin-resistant clone of 600 assayed was found to harbor a homologous recombinant, and this clone was expanded and transfected with the hygromycin B–resistance vector. Colonies were selected in hygromycin B (0.1 mg/ml). One clone of 940 assayed had a homologous recombinant of the second p53 allele.

这种细胞是完全敲除的，目前经常使用的干扰方法能实现目的基因的下调，而不能实现完全敲除。
这种完全敲除的方法一般都是用同源重组的方法替换基因组上的exon区序列。

p53缺失，一些细胞株是人为敲除的，也有细胞株是天然的p53缺失