DNA chromosomes

Most plasmids are topologically closed circles of DNA. They can be separated from the bulk of the chromosomal DNA by virtue of their resistance to alkaline solution. The double-stranded stmcture of DNA is denatured at high pH, but because the two strands of the plasmid are topologically joined they are more readily renatured. This property is exploited in rapid procedures for the isolation of plasmid DNA from recombinant microorganisms (5,6). 

To achieve overproduction of phenylalanine, the micro-organism should be derepressed at the pheA level and free of inhibition at the arcG level. Both genes are located on the chromosomal DNA of the micro-organism and, by means of amino add analogues such as p-fluoro-DL-phenylalanine, it is possible to make (phenylalanine) feedback resistant mutants of E.cdi (pheA and oroF mutants). The following procedure can be used ... 

In higher eukaiyotes, most of the chromosomal DNA carries 5-methyl-cytidine residues located in CpG sequence motives. There is a close correlation between transcriptional inactivation and methylation. On the other hand, considerable evidence shows that regions of DNA that are actively engaged in transcription lack 5-methyl-cytidine nucleotides in CpG motivs. Hence DNA methylation is a means how cells regulate gene expression. DNA methylation which is catalyzed by DNA methyltransferases is the best characterized epigenetic mechanism. 

Fig. 7. The nitrogen fixation (nif) genes of Klebsiella pneumoniae Eire contiguous on ca. 23 kb of chromosomal DNA. The EU rowheads indicate transcription stEuts.

Although bacteria have a single essential chromosome, one DNA molecule responsible for their genetic material, they may also contain extrachromosomal DNA. One variety of such DNA is viral DNA. This DNA can become incorporated into the chromosome and reproduced with it (lysogenic bacteria) or can become virulent — produced independently from the chromosome DNA — when it will cause lysis i.e. cell breakdown. The compound cis-[Pt(NH3)2Cl2] causes the change from... 

It is clear that both intact cell MALDI-TOF and PFGE have their limitations. PFGE analyses probes the chromosomal DNA of microorganisms for variations in the locations of specific restriction enzyme cleavage sites, while MALDI-TOF mass spectrometry of intact cells primarily examines abundant proteins such as ribosomal proteins35 and those associated with or near bacterial cell walls.58 In order for MALDI-TOF to detect a variation, a mutation must lead to noticeable changes in the expression of cell wall—associated... 

Southern hybridization experiments, employing the cloned PHA synthase structural gene of Acinetobacter sp. and sucrose gradient fractions of DNA preparations separated in plasmid and chromosomal DNA fractions gave two hybridization signals and revealed some but not yet conclusive evidence for... 

The construction of a shuttle vector (pSM73) which can be replicated both in Rhodococcus and in E. coli containing a gene reporter without its own promoter and on the cloning, before such gene, of random fragments of chromosomal DNA of Rhodococcus consists of ... 

Bacteria normally harbour a single, circular chromosome that tends to be tethered to the bacterial plasma membrane and tends to have few if any closely associated proteins. Many bacteria also contain extra-chromosomal DNA in the form of plasmids, as will be discussed later. Eukaryotes (plants, animals and yeasts) posses multiple linear chromosomes contained within a cell nucleus, and these chromosomes are normally closely associated with proteins termed histones (the pro-tein-DNA complex is termed chromatin). Eukaryotes also invariably possess DNA sequences within mitochondria and in chloroplasts in plants. The (usually circular) DNA molecules are much... 

An essential feature of the cloning vector used is that it must be capable of self-replication in the cell into which it is introduced, which is usually E. coli. Two of the most commonly used types of vector in conjunction with E. coli are plasmids and bacteriophage X. Plasmids are circular extra-chromosomal DNA molecules, generally between 5000 and 350 0000 bp in length, that are found naturally in a wide range of bacteria. They generally house several... 

Curiously, functions proposed for some brain KRPs [55] are very different from functions proposed for similar or identical KRPs in no-neuronal cells. For example, members of the kinesin-13 family have been implicated in both mitotic spindle function and in axonal membrane transport. Similarly, a mouse kinesin-4 was reported to associate with unidentified MBOs in neurites, but its chicken homolog bound to chromosomal DNA and mediates chromosome movements in the mitotic spindle. Finally, a kinesin-6 was originally found to have a role in mitotic spindle function, but members of the kinesin-6 family were also implicated in the transport of MTs into dendrites [56]. 

Simon, M. M. et al., UVB light induces a nuclear factor kB (NFkB) activity independently from chromosomal DNA damage in cell-free cytosolic extracts, J. Invest. Dermatol. 102, 422 127, 1994. 

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