Department of Botany and Plant Sciences, University of California, 92521-0124, Riverside, CA, USA.
Theor Appl Genet. 1993 Mar;86(1):121-7. doi: 10.1007/BF00223816.
Several studies have indicated a noncorrespondence between genetic and physical distances in wheat chromosomes. To study the physical distribution of recombination, polymorphism for C-banding patterns was used to monitor recombination in 67 segments in 11 B-genome chromosome arms of Triticum turgidum. Recombination was absent in proximal regions of all chromosome arms; its frequency increased exponentially with distance from the centromere. A significant difference was observed between the distribution of recombination in physically short and physically long arms. In physically short arms, recombination was almost exclusively concentrated in distal segments and only those regions were represented in their genetic maps. In physically long arms, while a majority of the genetic distance was again based upon recombination in distal chromosome segments, some interstitial recombination was observed. Consequently, these regions also contributed to the genetic maps. Such a pattern of recombination, skewed toward terminal segments of chromosomes, is probably a result of telomeric pairing initiation and strong positive chiasma interference. Interference averaged 0.81 in 35 pairs of adjacent segments and 0.57 across the entire recombining portions of chromosome arms. The total genetic map lengths of the arms corresponded closely to those expected on the basis of their metaphase-I chiasma frequencies. As a consequence of this uneven distribution of recombination there can be a 153-fold difference (or more) in the number of DNA base pairs per unit (centiMorgan) of genetic length.
几项研究表明，小麦染色体的遗传距离和物理距离之间存在不对应性。为了研究重组的物理分布，利用 C-带型多态性监测了 11 条 B 基因组染色体臂的 67 个片段中的重组。所有染色体臂的近端区域都没有重组；其频率随距着丝粒的距离呈指数增长。在物理上短臂和长臂的重组分布之间观察到显著差异。在物理上短臂中，重组几乎完全集中在远端片段，并且只有这些区域在其遗传图谱中表示。在物理上长的臂中，虽然大部分遗传距离仍然基于远端染色体片段的重组，但观察到一些间质重组。因此，这些区域也有助于遗传图谱。这种偏向于染色体末端片段的重组模式可能是端粒配对起始和强阳性交叉干扰的结果。干扰平均值为 0.81 在 35 对相邻片段和 0.57 在整个染色体臂的重组部分。臂的总遗传图谱长度与基于中期 I 交叉频率的预期值非常吻合。由于这种重组的不均匀分布，每单位（厘摩尔）遗传长度的 DNA 碱基对数量可能存在 153 倍（或更多）的差异。
