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標題: Mapping the Centromere of Chromosome 1 and 9 by Using B-A Translocations in Maize
作者: 張淑貞
Chang, Shu-Jen
關鍵字: centromere
B-A translocation
crossing-over suppression
出版社: 分子生物研究所
摘要: The centromere of chromosome 1 and 9 on RFLP maps were determined by usingterminal deficiencies with breakpoints adjacent to the centromere. Theseterminal deficiencies were hypoploids of B-A translocations TB-1Sb, TB-1La,TB-9Sd and TB-9 Lc. One of the two of B-A translocation chromosomes,designated B-A carring the B centromere and an A chromosome arm, undergoes nondisjunction at the second pollen mitosis, to result in one sperm with twoB-As and the other sperm with none. After fertilization, the sperm without B-Afertilizes with the egg gives rise to a hypoploid embryo deficient for apaternal chromosome arm.Mapping a centromere requires a prior determination of the position of RFLPmakers around the centromeric region in relation to the breakpoints ofhypoploids by Southern hybridization. The centromere is located between thetwo markers distal but closest to the breakpoints of B-A translocationassociated with the short and long arm of a chromosome. Results of this studymap the centromere of chromosome 1 in the umc167-um177a region and that ofchromosome 9 in the umc81-umc20 region. Anthoer intriguing result is thefinding of frequent rearrangements associated with three out four B-Atranslocations induced by x-irradiation. The reduction of crossing-overfrequency around the centromere was also discussed.
本研究以斷裂點最靠近中節的末端缺失,標定玉米第一及第九對染色體中 節在RFLP圖譜上的位置.這些末端缺染色體,分別為B-A易位染色體TB-1Sb, TB-1La,TB-9Sd及TB-9Lc之亞倍體.亞倍體是由於B-A易位染色體之B-A染色 體(帶B之中節及一個A染色體臂)在花粉第二次有絲分裂時不分離,造成一 個精細胞含兩個B-A而另一個精細胞不含任何B-A染色體.授粉時,後者與卵 細胞結合而形成亞倍體,故亞倍體缺失一個父本染色體臂.以亞倍體確定中 節位置時,需先以南氏雜合分析,確定中節附近RFLP標誌與長短臂之亞倍體 斷裂點的相對位置,而中節即位於長短臂上最靠近斷裂點之外側標誌之間. 本論文結果確定第一對染色體中節位在umc167和umc177a之間,第九對染色 體中節位在umc81和umc20之間.另外,亦發現X-ray誘導在B-A易位染色體斷 裂點附近的重新排列現象.並對於中節區域交換頻率降低的情形加以討論.
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