CYTOGENETICS OF MEIOSIS OF MAIZE

我们的目标是了解染色体分离的机制。 减数分裂，特别是同源染色体配对的开始。 玉米雄性中性粒细胞是唯一一个有大量 收集影响减数分裂的突变，并有可能做到 一流的细胞学。我们已经证明配对是在 细线型和合线型之间的转变，并与 染色体形态的一过性变化。我们称这一阶段为预演 合格线。我们将描述染色体结构的变化和 在减数分裂前期发生的核内排列，使用 John Sedat和他开发的计算机光学显微镜工作站 大卫·阿加德(加州大学旧金山分校)，能够记录三维图像 固定细胞和活细胞中的多种细胞成分。这个 独特的染色单体、染色单体、旋钮和着丝粒以及 使用染色探针、端粒探针、单个基因的探针 而荧光原位杂交(FISH)将使我们能够识别 每一个单独的染色体臂。我们将遵循一个人的行为 与其同源基因配对的同一染色体的区域。此数据 还将用于绘制玉米基因组的细胞学图谱。我们 将使用抗体来对抗功能重要的蛋白质，这些蛋白质涉及 重组来描述它们在配对过程中的位置。我们还将 开发研究活细胞配对的方法。这一分析将 使我们能够理解与核包膜相关的 端粒移动到配对的启动和定位上的位点 配对开始的染色体。我们会培养小细胞或者 花药和确定是否使用微管解聚剂 在前合子干扰端粒运动和配对的过程中 进程。我们将分析在启动过程中有缺陷的突变的微核细胞 配对以确定是否有任何前合子异常 染色体形态或端粒异常聚集。分析 突变体最终将允许我们将染色体形态的变化联系起来 和分布到相应的分子事件所需的 同源识别和突触。我们正在继续一项筛选计划 诱变新的减数分裂突变体的分离和细胞学特征 Mu或Ac转座子诱变。我们的首要任务是找到新的 在配对过程中有缺陷的突变体。 减数分裂对于所有有性繁殖的有机体和 这里描述的研究将进一步加深我们对这一过程的理解 只存在于玉米中，但存在于所有有机体中。减数分裂的机制是一个话题。 由于染色体分离不准确，具有重大的医学价值 (非整倍体)是几种先天性畸形和一种主要的 提前终止妊娠的原因。更好的理解 对玉米减数分裂的研究将使我们了解玉米减数分裂异常的基础 人类配子产生过程中的染色体分离。

Our goal is to understand the mechanism of chromosome segregation during meiosis, particularly initiation of pairing of homologous chromosomes. The maize male meiocyte is the only cell where there is a large collection of mutants that affect meiosis, and it is possible to do superb cytology. We have shown that pairing is initiated at the transition between leptotene and zygotene and is associated with transitory changes in chromosome morphology. We call this stage pre- zygotene. We will describe the changes in chromosome structure and arrangement in the nucleus that occur during meiotic prophase, using the computerized light microscope workstation developed by John Sedat and David Agard (UCSF) that is capable of recording three dimensional images of multiple cellular components in fixed and living cells. The distinctive chromomeres, chromomeres, knobs and centromeres along with the use of paining probes, telomere probes, probes for individual genes and fluorescence in situ hybridization (FISH) will allow us to identify each individual chromosome arm. We will follow the behavior of one region of the same chromosome as it pairs with its homolog. This data will also be used to develop a cytological map of the maize genome. We will use antibodies against functionally important proteins involved in recombination to describe their location during pairing. We will also develop methods to study pairing in living cells. This analysis will allow us to understand the relevance of nuclear envelope associated telomere movements to initiation of pairing and locate the sites on chromosomes where pairing is initiated. We will culture meiocytes or anthers and determine whether microtubule depolymerizing agents applied during prezygotene interfere with telomere movements and the pairing process. We will analyze mutant meiocytes defective in the initiation of pairing to determine whether any of the have abnormal pre-zygotene chromosome morphology or abnormal telomere clustering. Analysis of mutants will eventually allow us to link changes in chromosome morphology and distribution to the corresponding molecular events required for homology recognition and synapsis. We are continuing a screening program to isolate and cytologically characterize new meiotic mutants induced by Mu or Ac transposon mutagenesis. Our highest priority is to find new mutants deficient in the pairing process. Meiosis is essential for all sexually reproducing organisms and the studies described here will further our understanding of this process not only in maize but in all organisms. The mechanism of meiosis is a topic of major medical interest since inaccurate chromosome segregation (aneuploidy) is causal in several congenital malformations and a major cause of premature termination of pregnancy. An improved understanding of meiosis in maize will allow us to understand the basis of abnormal chromosomal segregation during human gamete production.