G what is the role of 2'-3'-dideoxynucleoside triphosphates in the chain termination method of dna sequencing?

2'-3' dideoxynucleoside triphosphates (2'-3'ddNTP) are similar to deoxynucleoside triphosphate (dNTP) except 3'-OH group which is absent in 2'-3' ddNTP. The 3'-OH group is the site where new dNTPs are added by DNA polymerase enzyme.

The absence of 3'-OH group in ddNTP results in the formation of truncated DNA fragments. These fragments are analysed in the DNA sequencing process.