Progress of gene targeting in mouse

Gene targeting is a powerful approach of studying the gene function in vivo. Specific genetic modifications, including simple gene disruption, point mutations, large chromosomal deletions and rearrangements, targeted incorporation of foreign genes, could be introduced into the mouse genome by gene targeting. Recent studies make it possible to do the gene targeting with temporal and spatial control.     

广义酵母的染色体核型分析与基因组进化

采用脉冲场强凝胶电泳技术对4种34个Saccharomyces属广义酵母样本的染色体核型进行了分析,观察到丰富的染色体数目和大小的多态性．染色体数目在所研究的广义酵母中从8到16都有出现,但小于0．5Mb的染色体仅见于Saccharomyces exiguus．广义酵母染色体数目和大小的多态在所受试样品中普遍出现,表明在进化过程中酵母基因组发生了迅速而广泛的重排．     

分别用空气、O_2、N_2、CO_2加压对洋葱根尖细胞的影响初探

初次研究了用空气、O_2、N_2、CO_2加压对洋葱(Allium cepa L.)根尖细胞的影响,发现洋葱根尖经不同气体加压处理后,其间期细胞和分裂期细胞的形态和结构有显著的变化。在分裂间期的细胞中,有的细胞核出芽一形成核上小核;有的细胞核分解,形成数个微核。在分裂期的细胞中,染色体出现各种畸变(如缺失、断片、染色体环、双着丝点染色体等);染色体的数目亦有变化;有丝分裂时不均等分裂,染色体桥,落后染色体也大量存在。实验表明,气压(空气、O_2、CO_2、N_2)对间期细胞和分裂期细胞的结构及行为有影响。不同的气体成分对间期细胞和分裂期细胞结构和行为的影响程度不同。     

Rapid diagnosis with FISH for chromosomal abnormality of fetal pyelectasia

Fluorescence in situ Hybridization （FISH） was used to investigate whether the chromosome of the fetus prenatally diagnosed as pyelectasis was normal or not. Amniotic fluid was taken from the pregnant woman whose fetus was detected with pyelectasia by prenatal examination. The chromosome of the amniotic fluid cell without culture was examined with FISH. The result shows that compared with the traditional amniotic fluid cell culture, FISH has the advantages of more rapid, higher sensitivity and specificity, and was 10-12 days earlier to complete the diagnosing than the traditional method. The fetuses detected chromosomal abnormality in each groups were induced during the middle and late trimester, while those fetuses with normal chromosome continued pregnancy, the rate of spontaneous disappearance of pyelectasia decreased as the severity of pyelectasia increased. FISH can satisfy the urgent need in the clinical prenatal diagnosis due to its rapidity to determine whether fetus with pyelectasia was accompanied with chromosomal.     

Chromsome aberrations in cattle raised on bracken fern pasture

Summary Thirteen cows maintained on natural bracken fern (Pteridium aquilinum) were analyzed cytogenetically. The frequency of structural chromosome aberrations detected in peripheral blood cells was significantly higher when compared to that detected in animals raised on pasture containing no bracken fern. We discuss the clastogenic action of fern and its synergistic action with infection by type 2 and 4 papilloma virus in the same animals.Acknowledgments. We are grateful to Dr F. J. Benesi, Dr J. L. Guerra and Dr I. L. Sinhorini for performing some of the clinical and pathological analyses; O. P. Ferraz, L. A. Tadeu Dias, L. F. Feitosa and A. M. N. Paiva for technical assistance; and to Dr N. H. C. Castro and Dr C. de Araujo Peres for critical and statistics review, respectively. Research was supported by CNPq FAPESP and CAPES.     

植物B染色体传递的遗传控制

植物B染色体传递的规律与A染色体不同,B染色体的传递是非孟德尔式的,其遗传控制甚为复杂.植物B染色体传递率可区分为高和低2种,它们是受基因控制的,与B染色体在减数分裂过程中的行为无关.在一些材料中,控制B染色体传递率的基因处在A染色体上,而在另一些材料中却是在B染色体上.     

Genotoxic effects of dithane M-45 on the bone marrow cells of mice in vivo

Summary Genotoxic effects of dithane M-45 were studied on the bone marrow cells of male albino mice (Lacca strain) in vivo. Different doses (30 mg, 40 mg and 300 mg/kg b.wt) of dithane M-45 were injected intraperitoneally and their effects were investigated after time intervals of 1, 2, 5 and 10 days. The chromosomal aberrations observed in the bone marrow cells of male mice after treatment with dithane M-45 were fragments, rings, dicentric chromosomes, terminal chromatid deletions, chromatid gaps and breaks. In addition to these chromosomal aberrations, physiological effects such as uneven stretching of chromatin material, end-to-end chromosomal associations, exchange configurations, clumping, stickiness and centromeric associations were also observed.     

CO_2激光对蚕豆诱变效应试验研究

本试验采用功率密度为394mW/cm2的CO2激光照射蚕豆萌动种子，观察其对蚕豆极尖细胞染色体畸变及幼苗生长的影响，探讨CO2激光照射后蚕豆植株农艺性状的变异及其遗传传递情况，试验结果表明：CO2激光不同时间照射蚕豆萌动种子，均能使根尖细胞产生染色体畸变，且畸变类型相似。同时，对L1功苗生长有明显的抑制作用，L2植株高度，。分枝数及结荚数等农艺性状均产生不同程度的，其中分枝数这一性状的变异性能传递给L3，其余性状的变异则属生理损伤所致。