ddNTPresistant

ddNTPresistant refers to a phenomenon observed in certain molecular biology techniques, particularly DNA sequencing, where the normal process is impeded by the presence of dideoxynucleotide triphosphates (ddNTPs). ddNTPs are chain-terminating nucleotides that are crucial for Sanger sequencing. They lack a hydroxyl group at the 3' carbon, which prevents the formation of a phosphodiester bond with the next incoming nucleotide, thereby halting DNA synthesis.

In standard Sanger sequencing, a controlled amount of ddNTPs is added along with dNTPs. When a ddNTP is incorporated into the growing DNA strand, that strand terminates. By using ddNTPs labeled with different fluorescent dyes, the sequence of the DNA can be determined based on the color of the terminal label at each position.

The term "ddNTPresistant" implies a situation where the incorporation of ddNTPs is less efficient than expected or does not occur properly. This can lead to incomplete or inaccurate sequencing reads. Factors contributing to ddNTP resistance can include altered enzyme kinetics of the DNA polymerase, suboptimal buffer conditions, or unusual structural features of the DNA template itself that hinder the polymerase's ability to incorporate the ddNTP. In some cases, specific mutations within the polymerase gene might also confer a degree of ddNTP resistance. Understanding and overcoming ddNTP resistance is important for optimizing DNA sequencing protocols and ensuring reliable results.