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Bacteria that are growing logarithmically differ from stationary phase bacteria with regard to the number of genome copies present in the cell, and this has implications for the ability to carry out an important DNA repair process. During logarithmic growth, two or more copies of any particular region of the chromosome are ordinarily present in ...
Usually, a single bacterial chromosome is present, although some species with multiple chromosomes have been described. [5] Along with chromosomal DNA, most bacteria also contain small independent pieces of DNA called plasmids that often encode advantageous traits but are not essential to their bacterial host.
The term "genome" usually refers to the DNA (or sometimes RNA) molecules that carry the genetic information in an organism, but sometimes it is uncertain which molecules to include; for example, bacteria usually have one or two large DNA molecules (chromosomes) that contain all of the essential genetic material but they also contain smaller ...
Artificial chromosomes are manufactured chromosomes in the context of yeast artificial chromosomes (YACs), bacterial artificial chromosomes (BACs), or human artificial chromosomes (HACs). An artificial chromosome can carry a much larger DNA fragment than other vectors. [9] YACs and BACs can carry a DNA fragment up to 300,000 nucleotides long.
The vast majority of chromid-encoding bacteria only have a single chromid, although 9% have more than one (compared with 12% of megaplasmid-encoding bacteria containing multiple megaplasmids). The genus Azospirillum contains three species which have up to five chromids, the most chromids known in a single species to date.
Microbes are ideally suited for biochemical and genetics studies and have made huge contributions to these fields of science such as the demonstration that DNA is the genetic material, [49] [50] that the gene has a simple linear structure, [51] that the genetic code is a triplet code, [52] and that gene expression is regulated by specific ...
The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [11] [12] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
There are many exceptions to this; for example, some Streptomyces and Borrelia species contain a single linear chromosome, [129] [130] while some bacteria including species of Vibrio contain more than one chromosome. [131] [132] Some bacteria contain plasmids, small extra-chromosomal molecules of DNA that may contain genes for various useful ...