Final answer:
Incorporation of any ddNTP, such as ddATP, ddCTP, ddTTP, or ddGTP, would result in chain termination during DNA sequencing, as employed in the dideoxy chain termination method developed by Fred Sanger.
Step-by-step explanation:
Incorporation of ddNTPs (dideoxynucleotide triphosphates) would result in chain termination during DNA sequencing. The options given, a) ddATP, b) ddCTP, c) ddTTP, and d) ddGTP, are all forms of ddNTPs, and each is capable of terminating the DNA chain when incorporated.
The method employing ddNTPs is known as the dideoxy chain termination method, developed by Fred Sanger. In this method, sequence analysis is carried out by synthesizing DNA strands in the presence of a mixture of normal deoxynucleotides (dNTPs) and a small proportion of ddNTPs.
Each ddNTP lacks a 3' hydroxyl group (3' OH), which is essential for forming a phosphodiester bond with the next nucleotide. Therefore, when a ddNTP is incorporated into the DNA strand, no further nucleotides can be added, resulting in termination of chain elongation.