Primed synthesis fragment primers

Figure 4.26 (a) DNA replication at low resolution (for example as seen by electron microscopy). Only one replication fork is visible and it appears that both strands of the parental DNA replicate continuously in the same direction, which cannot be the case, since the two strands of parental DNA are anti-parallel, (b) The problem is solved by the priming of DNA synthesis with short RNA primers, whose 3 -hydroxyl can be used by DNA polymerase, producing Okazaki fragments, while on the other strand, DNA synthesis is continuous. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)... 

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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