Practice question

In DNA polymerization, α-phosphate of deoxynucleoside triphosphate is incorporated into growing phosphodiester backbone, while β and γ phosphates are released as pyrophosphate driving reaction forward. Therefore α-32P-dNTP results in internally labeled products detectable by autoradiography, and 5' end-labeling uses γ-32P-ATP via polynucleotide kinase to label primer terminus. Gamma-32P-labeled dNTP cannot be internally incorporated because γ-phosphate is not retained in final strand; polymerase requires cleavage between α and β phosphates. Consequently, experiments requiring internal radioactive tracing cannot utilize gamma-labeled precursors, distinguishing end-labeling from incorporation strategies in labeling techniques.