Determination of nucleotide sequences in DNA
Determination of nucleotide sequences in DNA
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DOI:
10.1007/bf01115145
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发表时间:
1981
影响因子:
4
通讯作者:
F. Sanger
中科院分区:
文献类型:
--
作者:
F. Sanger
with, a region on the DNA being sequenced (the template). Mononucleotide residues are added sequentially to the 3'end of the primer from the corresponding deoxynucleoside triphosphates, making a complementary copy of the template DNA. By using triphosphates containing 32p in the cz position, the newly synthesized DNA can be labelled. In the early experiments synthetic oligonudeotides were used as primers, but after the discovery of restriction enzymes it was more convenient to use fragments resulting from their action as they were much more easily obtained.The copying procedure was used initially to prepare a short specific region of labelled DNA which could then be subjected to partial digestion procedures. One of the difficulties of sequencing DNA was to find specific methods for breaking it down into small fragments. No suitable enzymes were known that would recognize only one nucleotide. However, Berg, Fancher, and Chamber] in (7) had shown earlier that under certain conditions it was possible to incorporate ribonucleotides, in place of the normal deoxyribonucleotJdes, into DNA chains with DNA polymerase. Thus, for instance, if copying were carried out using ribo CTP and the other three deoxynucleoside triphosphates, a chain could be built up in which the C residues were in the ribo form. Bonds involving ribonucleotides could be broken by alkali under conditions where those involving the deoxynucleotides were not, so that a specific splitting at C residues could be obtained. Using this method we were able to extend our sequencing studies to some extent (g). However, extensive fractionations and analyses were still required.