LOH

LOH一般都與腫瘤的抑制基因（如p53）有關，在兩個等位基因都存在時，會抑制惡性腫瘤的發生。而當一個等位基因明顯異常或缺失時（另一個等位基因已經處於沒有活性的狀態）不再發生抑制惡性狀態，細胞就轉化為癌細胞。常見於視網膜母細胞瘤、乳腺癌和其他由於腫瘤抑制基因突變而引起的癌症。

LOH(loss of heterozygosity)雜合性缺失: ：Loss of a normal allele from a region of one chromosome of a pair, allowing a defective allele on the homologous chromosome to be clinically manifest. A feature of many cases of retinoblastoma, breast cancer, and other tumors due to mutation in a TSG.