Fu Huihua, Zheng Zhenwei, Dooner Hugo K
The Waksman Institute, Rutgers University, Piscataway, NJ 08855, USA.
Proc Natl Acad Sci U S A. 2002 Jan 22;99(2):1082-7. doi: 10.1073/pnas.022635499. Epub 2002 Jan 15.
Genetic map length and gene number in eukaryotes vary considerably less than genome size, giving rise to the hypothesis that recombination is restricted to genes. The complex genome of maize contains a large fraction of repetitive DNA, composed principally of retrotransposons arranged in clusters. Here, we assess directly the contribution of retrotransposon clusters and genes to genetic length. We first measured recombination across adjacent homozygous genetic intervals on either side of the bronze (bz) locus. We then isolated and characterized two bacterial artificial chromosome clones containing those intervals. Recombination was almost 2 orders of magnitude higher in the distal side, which is gene-dense and lacks retrotransposons, than in the proximal side, which is gene-poor and contains a large cluster of methylated retrotransposons. We conclude that the repetitive retrotransposon DNA in maize, which constitutes the bulk of the genome, most likely contributes little if any to genetic length.
真核生物的遗传图谱长度和基因数量的变化远小于基因组大小，由此产生了重组仅限于基因的假说。玉米复杂的基因组包含很大一部分重复DNA，主要由成簇排列的反转录转座子组成。在这里，我们直接评估反转录转座子簇和基因对遗传长度的贡献。我们首先测量了青铜（bz）基因座两侧相邻纯合遗传区间的重组情况。然后，我们分离并鉴定了包含这些区间的两个细菌人工染色体克隆。在基因密集且缺乏反转录转座子的远端，重组率几乎比基因贫乏且含有一大簇甲基化反转录转座子的近端高2个数量级。我们得出结论，构成基因组大部分的玉米重复反转录转座子DNA对遗传长度的贡献即使有也很可能微乎其微。
