Mizuno K, Vincek V, Figueroa F, Klein J
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Federal Republic of Germany.
Immunogenetics. 1989;30(2):112-8. doi: 10.1007/BF02421539.
Recombination in the proximal region of mouse chromosome 17 is greatly reduced in heterozygotes carrying the wild-type and the t complex-type chromosomes. The reason for this is the presence of two non-overlapping inversions in the t complex. Rare crossing-over does, however, occur within the t complex of the t/+ heterozygotes. Here we characterize four such exceptional intra-t recombinants, tTu1 through tTu4. To map the positions of the genetic exchange in these four recombinants, we analyzed them with DNA probes specific for 16 loci distributed over the t complex. The analysis revealed that in three of the four recombinants, an equal crossing-over occurred in the short region between the two inversions, producing chromosomes carrying either the proximal inversion only (tTu1 and tTu4) or the distal inversion only (tTu2). In the fourth recombinant (tTu3), unequal crossing-over occurred within the proximal inversion between loci D17Leh119 and D17Leh66, producing a chromosome in which the region containing loci Tcp-1, T, and D17Tu5 has been duplicated. The duplication of the Brachyury locus leads to the suppression of the tail-shortening effect normally produced by the interaction of the dominant (T) and recessive (tct) alleles at this locus so that the T/tTu3 mice have normal tails.
在携带野生型和t复合体型染色体的杂合子中，小鼠17号染色体近端区域的重组大大减少。原因是t复合体中存在两个不重叠的倒位。然而，在t/+杂合子的t复合体内确实会发生罕见的交叉互换。在此，我们鉴定了四个这样的特殊t复合体内重组体，即tTu1至tTu4。为了定位这四个重组体中基因交换的位置，我们用分布在t复合体上的16个位点的特异性DNA探针分析了它们。分析表明，在四个重组体中的三个中，在两个倒位之间的短区域发生了均等交叉互换，产生了仅携带近端倒位（tTu1和tTu4）或仅携带远端倒位（tTu2）的染色体。在第四个重组体（tTu3）中，在近端倒位内的D17Leh119和D17Leh66位点之间发生了不等交叉互换，产生了一条染色体，其中包含Tcp-1、T和D17Tu5位点的区域被重复。短尾基因座的重复导致了通常由该基因座上显性（T）和隐性（tct）等位基因相互作用产生的尾巴缩短效应受到抑制，因此T/tTu3小鼠具有正常的尾巴。
