2 ,3 -dideoxynucleoside triphosphate ddNTP

DNA polymerases normally use 3 -deoxynucleotide triphosphates as substrates for polymerization. Given an adequate concentration of substrate, DNA polymerase synthesizes a long strand of new DNA complementary to the substrate. The use of this reaction for sequencing DNA depends on the inclusion of a single 2/3 -dideoxynucleoside triphosphate (ddNTP) in each of four polymerization reactions. The dideoxynucleotides ate incorporated normally in the chain in response to a complementary residue in the template. Because no 3 -OH is available for further extension, polymerization is... 

Nucleotides 2 -deoxynucleoside triphosphates (dNTPs) are purchased from Sigma (St. Louis, MO), and the 2, 3 -dideoxynucleoside triphosphates (ddNTPs) from Boehringer-Mannheim Biochemicals (Mannheim, Germany)... 

The key to the chain termination method is the addition of a 2, 3 -dideoxynucleoside triphosphate (ddNTP) to the synthesizing medium ... 

In molecular biology, TDT is used to effect the addition of complementary homopolymeric tails to vector and complementary DNA (cDNA) obtained from a mature mRNA template by reverse transcription and PCR amplification. An alternative application of TDT involves labehng of the 3 termini of DNA fragments with a P-labeled dNTP [36], a dideoxynucleoside triphosphate (ddNTP) [37], or a ribonucleoside triphosphate (rNTP) [38]. 

Dideoxynucleoside Triphosphate (ddNTP) Nucleotide lacking the 3 -hydroxyl function on its de-oxyribose sugar required for formation of bonds between nucleotides. 

A number of nucleotide analog compounds function by blocking further chain growth at the replication fork. The 2 3 -dideoxynucleosides can be converted to the triphosphates (ddNTPs). In the case of bacteria, these are incorporated onto the 3 -hydroxyl end of a growing DNA chain, and because the new end now lacks a 3 hydroxyl, no further additions can occur. They are used in conjunction with DNA polymerase I in the dideoxy method of Sanger for determining DNA sequences. 

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