Patent ID: 7838226

Claim:
A method of measuring DNAs comprising the steps of: contacting a gold electrode of a field effect transistor with a measurement solution containing DNA polymerase, DNA probes are immobilized on a surface of the gold electrode, wherein the gold electrode is connected to a gate of the field effect transistor with a conductive wire; applying a high-frequency voltage having a frequency greater than or equal to 1 kHz and at a constant amplitude, between the gold electrode and a reference electrode contacting with the measurement solution; injecting sample DNAs into the measurement solution thereby binding the sample DNAs to the DNA probes; injecting into the measurement solution at least one type of deoxyribonucleoside triphosphate selected from a group consisting of dATP, dCTP, dGTP, and dTTP, or at least one type of deoxyribonucleoside triphosphate derivatives after finishing the step of injecting sample DNAs for a predetermined period of time, thereby enzymatically extending the DNA probes; measuring an electric characteristic change of the transistor either before and after binding the sample DNAs to the DNA probes, or before and after extension of the DNA probes; and detecting any of presence/absence of the sample DNAs bound to the DNA probes, based upon the measured electric characteristic change of the transistor.