Restriction endonuclease genes

Figure 12.10 Some genes and restriction sites on the E. coli plasma pBR322. Eco RI, Pst I, and Sal I are restriction endonucleases and the sites cleaved by these enzymes.

Approaches to cloning DNA Genomic DNA Restriction endonucleases fragment DNA Total nuclear DNA cloned Genes contain introns cDNA Reverse transcription of mRNAs from cell Genes expressed cloned Genes have no introns... 

To isolate a gene, scientists use surgical DNA scissors called restriction endonucleases (RE), proteins made by bacteria that cut DNA, based on specific rules. Each kind of RE—there are hundreds— recognizes specific sequences of 4-8 base pairs and cuts the DNA molecule at a specific spot (Figure 1.2). The biotechnologist selects... 

Key enzymes in gene cloning include restriction endonucleases (especially the type II enzymes) and DNA ligase. 

The study of catabolic plasmids involves analysis of both structural and regulatory genes and the enzymatic activities of the gene products. Catabolic plasmids that specify similar enzymatic activities often have similar restriction endonuclease fragmentation patterns, and regions of homologous DNA. 

A vector is a molecule of DNA to which the fragment of DNA to be cloned is joined. Essential properties of a vector include 1) it must be capable of autonomous replication within a host cell, 2) it must contain at least one specific nucleotide sequence recognized by a restriction endonuclease, and 3) it must carry at least one gene that confers the ability to select for the vector, such as an antibiotic resistance gene. Commonly used vectors include plasmids and bacterial and animal viruses. 

A restriction map of plasmid pBR322 indicating the positions of its antibiotic resistance genes and the sites of nucleotide sequences recognized by specific restriction endonucleases. 

This child is unaffected and shows only fragment a when DNA is digested with the same restriction endonuclease as her parent s DNA. Thus, the normal gene is associated with the polymorphism giving fragment "a. ... 

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