Justice M J, Bode V C
Division of Biology, Kansas State University, Manhattan 66506.
Genetics. 1988 Oct;120(2):533-43. doi: 10.1093/genetics/120.2.533.
The t region of mouse chromosome 17 exhibits recombination suppression with wild-type chromatin. However, the region has resisted classical genetic dissection because of a lack of defined variants. Mutations induced by N-ethyl-N-nitrosourea (ENU) at the Brachyury (T), quaking (qk), and tufted (tf) loci of the mouse tw5 haplotype have now allowed the analysis of crossovers between two complete t haplotypes. A classical breeding analysis of the complete t haplotypes, tw5 and t12, utilizing the newly induced markers, reveals two inversions in t chromatin: one involving T and qk, and one involving tf and the H-2 complex. Moreover, the recombination frequency between the loci of T and qk is reduced compared to the frequency reported in normal chromatin. These two inversions are a sufficient explanation for the recombination inhibition with normal chromatin exhibited by t haplotypes isolated from the wild. Furthermore, the reduced recombination frequency between T and qk may indicate that the proximal gene rearrangement is not a simple inversion.
小鼠17号染色体的t区域与野生型染色质表现出重组抑制。然而，由于缺乏明确的变异，该区域一直难以进行经典的遗传剖析。现在，通过在小鼠tw5单倍型的短尾（T）、颤抖（qk）和簇状（tf）位点由N-乙基-N-亚硝基脲（ENU）诱导产生的突变，得以分析两个完整t单倍型之间的交叉情况。利用新诱导的标记对完整的t单倍型tw5和t12进行经典的育种分析，揭示了t染色质中的两个倒位：一个涉及T和qk，另一个涉及tf和H-2复合体。此外，与正常染色质中报道的频率相比，T和qk位点之间的重组频率降低。这两个倒位足以解释从野生环境中分离出的t单倍型与正常染色质之间表现出的重组抑制现象。此外，T和qk之间降低的重组频率可能表明近端基因重排并非简单的倒位。
