Primed synthesis principle

Principle of the plus and minus method (i) Primed synthesis... 

To prepare compounds, you must use reactions that (by the principles just outlined) are predicted to "go." Not all reactions that take place, however, are suitable for synthesis, and attention must be paid to purity of product, cost of reactants, and ease of preparation. We comment on these factors in the answers to the A problems, and in the following discussion of the preparation of a compound X. If your laboratory work includes qualitative analysis, you might well consider each evolved gas and each precipitate to be a chemical preparation, even though the prime purpose of the project before you is separation or identification. 

Biotinylated dUTP can also be used to label DNA probes by a different method, namely random-primed labeling (4). The principle of this method is based on the reannealing of hexadeoxyribonucleotide primers, which have random specificity, to the denatured DNA strands. The DNA to be labeled has to be linearized and denatured before the strands are used as templates in the labeling reaction. The complementary strands are synthesized from the 3 OH termini of the reannealed hexanucleotides by the Klenow fragment of E. coli DNA polymerase I. The primers reanneal at random sites of the template strands, so that the synthesis of the complementary strands is primed at random sites. If one of the deoxyribonucleoside triphosphates present in the reaction mixture is labeled, the newly synthesized strands will become labeled by the incorporation of the labeled nucleotides. The end product of this reaction is a mixture of unlabeled (template) and labeled... 

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