Mapping the Centromere of Chromosome 1 and 9 by Using B-A Translocations in Maize

• Main Authors: Chang, Shu-Jen, 張淑貞
• Other Authors: Bor-Yaw Lin
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/26288808330520306462

碩士 === 國立中興大學 === 分子生物研究所 === 85 === 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.