Restriction fragments, joining

Therefore, DNA restriction fragments having such sticky ends can be joined together to create new combinations of DNA sequence. If the fragments are derived from DNA molecules of different origin, novel recombinant forms of DNA are created. 

These cohesive ends can be used to join together different restriction fragments. It is easy to see that the complementary single-stranded tails can form base pairs to regenerate the original hexanucleotide... 

DNA ligase repairs broken DNA by joining two nucleotides in a DNA strand. It is commonly used in genetic engineering to do the reverse of a restriction enzyme that is, to join together complementary restriction fragments. While sticky ends allow two complementary restriction... 

Two restriction fragments with complementary ends can be joined with DNA ligase to form a recombinant DNA (see Figure 9-11). 

Thiazole green represents another class of carbocyanines, which was recently utilized in the low-level detection of DNA restriction fragments by Soper et al. [74]. This dye is comprised of a quinolinium and a thiazolium nucleus joined by a pen-tamethine chain. The synthetic route to the thiazole green 34 is shown in Fig. 14.7. 2-Methylbenzothiazole 29 was allowed to react with methyl iodide to give the N-methyl derivative 30 which was further treated with malonaldehyde-dianil hydrochloride to afford the intermediate product 31. The intermediate product 31 was then allowed to react with N-(3-iodopropyl)lepidinium iodide 33, which had been obtained from the reaction of lepidine with 1,3-diiodopropane, to finally afford the asymmetrical thiazole green 34. 

Fig. 24.3 The construction of a chimeric (or recombinant) DNA molecule hy joining together two DNA fragments produced by cleavage of different parental DNA molecules with the same restriction endonuclease.

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. 

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