Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Luminescent chemodosimeters for bioimaging.

The amyloid beta protein has been identified as an important component of both cerebrovascular amyloid and amyloid plaques of Alzheimer9s disease and Down syndrome. A complementary DNA for the beta protein suggests that it derives from a larger protein expressed in a variety of tissues. Overexpression of the gene in brain tissue from fetuses with Down syndrome (trisomy 21) can be explained by dosage since the locus encoding the beta protein maps to chromosome 21. Regional localization of this gene by both physical and genetic mapping places it in the vicinity of the genetic defect causing the inherited form of Alzheimer9s disease.

https://science.sciencemag.org/content/sci/235/4791/880.full.pdf

Amyloid beta protein gene: cDNA, mRNA distribution, and genetic linkage near the Alzheimer locus

Repetitive DNA sequences form a large portion of the genomes of eukaryotes. The 'selfish DNA' hypothesis proposes that they are maintained by their ability to replicate within the genome. The behaviour of repetitive sequences can result in mutations that cause genetic diseases, and confer significant fitness losses on the organism. Features of the organization of repetitive sequences in eukaryotic genomes, and their distribution in natural populations, reflect the evolutionary forces acting on selfish DNA.

The evolutionary dynamics of repetitive DNA in eukaryotes

The human XIST gene: analysis of a 17 kb inactive X-specific RNA that contains conserved repeats and is highly localized within the nucleus.

Every eukaryotic chromosome has a centromere, the locus responsible for poleward movement at mitosis and meiosis. Although conventional loci are specified by their DNA sequences, current evidence favors a chromatin-based inheritance mechanism for centromeres. The chromosome segregation machinery is highly conserved across all eukaryotes, but the DNA and protein components specific to centromeric chromatin are evolving rapidly. Incompatibilities between rapidly evolving centromeric components may be responsible for both the organization of centromeric regions and the reproductive isolation of emerging species.

https://science.sciencemag.org/content/sci/293/5532/1098.full.pdf

The centromere paradox: stable inheritance with rapidly evolving DNA.

A number of applications of the detection of deoxyribonucleic acid synthesis by fluorescence microscopy are illustrated. These include (a) the analysis of sister chromatid exchanges and sister chromatid segregation at mitosis, (b) the location of chromosome regions containing deoxyribonucleic acid with an asymmetric distribution of thymine residues between polynucleotide chains and (c) the detection of late replicating regions in metaphase chromosomes. The suppression of 33258 Hoechst fluorescence by 5-bromodeoxyuridine incorporated biosynthetically into interphase nuclei is demonstrated both in fixed cytologic preparations and in unfixed cultured cells. Many of the cytologic observations described might form a basis for future biochemical studies.

Recent developments in the detection of deoxyribonucleic acid synthesis by 33258 Hoechst fluorescence

Mammalian chromosome structure

Evolution of alpha satellite.

BrdU-33258 Hoechst techniques have been used to characterize DNA replication patterns in lymphocytes from human females with supernumerary or structurally abnormal X chromosomes. Fluorescence analysis permits identification of late replicating X chromosomes in a very high proportion of cells and affords a high resolution method for determining the interchange points of X-X and X-autosome translocations. Asynchrony among terminal replication patterns of multiple late replicating X chromosomes within an individual cell can occasionally be demonstrated. The arms of isochromosomes usually exhibit symmetrical fluorescence patterns, with replication terminating in bands Xq21 and Xq23 (predominant pattern) or in bands Xq25 and Xq27 (alternative pattern) in both arms. In the vast majority of lymphocytes containing a balanced X-13 or X-19 translocation, the normal X is late replicating. However, DNA synthesis in the translocation products occasionally appears somewhat delayed relative to that expected for an early replicating X, consistent with possible position effects on replication kinetics.

Huntington F. Willard

Papers

Recent developments in the detection of deoxyribonucleic acid synthesis by 33258 Hoechst fluorescence

Mammalian chromosome structure

Evolution of alpha satellite.

BrdU-33258 Hoechst analysis of DNA replication in human lymphocytes with supernumerary or structurally abnormal X chromosomes.

Centromeres: the missing link in the development of human artificial chromosomes.