Here, the DNA-RNA hybrids synthesized in Stage 1 are converted into full-length double-stranded cDNAs. The primers for synthesis of second-strand cDNA are created by RNase H, which introduces nicks into the RNA moiety of the cDNA-mRNA hybrids. E. coli DNA polymerase I extends the newly created 3'-hydroxyl termini, using the first-strand cDNA as a template. - [Read Construction of cDNA Libraries Protocol]
Protocol describes a method for DNA fragmentation by nebulization, in which the fine mist created by forcing a DNA solution through a small hole in the nebulizer unit is collected. The size of the fragments obtained by nebulization is determined chiefly by the speed at which the DNA solution passes through the hole, altering the pressure of the gas blowing through the nebulizer, the viscosity of the solution, and the temperature. - [Read Fragmentation of DNA by Nebulization Protocol]
In this method, the nuclease BAL 31 is used to make uni- or bidirectional deletions in a segment of cloned DNA. BAL 31 is a complex enzyme and tends to digest a population of double-stranded DNA targets in an asynchronous fashion, Deletions created by BAL 31 are therefore far more heterogeneous in size than those created by processive enzymes such as exonuclease III. - [Read Generation of Bidirectional Sets of Deletion Mutants by Digestion with BAL 31 Nuclease Protocol]