Prokaryotic cells genome

There are two general kinds of cells those having a membrane-bounded nucleus called eukaryotic cells, and those without a nuclear envelope called prokaryotic cells. Humans have eukaryotic cells. All eukaryotic cells contain a nucleus that contains the genome, the complete set of genes. Unless noted otherwise, our discussion will be restricted to eukaryotic cells. 

Before one cell can divide into two cells, the cell must make a copy of the cellular DNA so that after cell division, each cell will contain a complete complement of the genetic material. Replication is the cellular process by which DNA or the cellular genome is duplicated with almost perfect (and sometimes perfect) fidelity. The replicative process in prokaryotic cells, such as Escherichia coli (E. coli) cells, is best understood and will be described in detail, and the aspects that differ in replicating eukaryotic cells will be noted. 

The size of the genomic DNA in eukaryotic cells (such as the cells of yeast, plants, or mammals) is much larger (up to 10+11 base pairs) than in E. coli (ca. 10+6 base pairs). The rate of the eukaryotic replication fork movement is about fifty nucleotides per second, which is about ten times slower than in E. coli. To complete replication in the relatively short time periods observed, multiple origins of replication are used. In yeast cells, these multiple origins of replication are called autonomous replication sequences (ARSs). As with prokaryotic cells, eukaryotic cells have multiple DNA polymerases. DNA polymerase S, complexed with a protein called proliferating... 

Before we study how genomic libraries are made we first need to understand the differences between the genetic organization in eukaryotic and prokaryotic cells. Bacterial genes are uninterrupted sequences of... 

DNA (section 2.4.1) than eukaryotic RNA (section 2.4.2). The result will be the construction of a collection of cloned DNA fragments propagated in bacteria that is called the genomic library. This library should contain representatives of every sequence in the chromosome of a prokaryotic cell and every expressed gene in the case of a eukaryotic cell. The final step consists of the screening of every recombinant clone to identify the required gene(s). 

The DNA of prokaryotes is not complexed with proteins in extensive arrays with specified architecture, as is the DNA of eukaryotes. In general, there is only a single, closed, circular molecule of DNA in prokaryotes. This circle of DNA, which is the genome, is attached to the cell membrane. Before a prokaryotic cell divides, the DNA replicates itself, and both DNA circles are bound to the plasma membrane. The cell then divides, and each of the two daughter cells receives one copy of the DNA (Figure 1.10). 

Every cell of any organism that is able to reproduce itself contains the fnll genetic instmction set that is known collectively as its genome, donhle-stranded DNA makes np this coded set. In prokaryotic cells... 

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