Final answer:
The phosphate groups in a deoxynucleoside triphosphate (dNTP) molecule provide the energy for DNA synthesis by releasing energy when they are cleaved off during DNA synthesis.
Step-by-step explanation:
The part of a deoxynucleoside triphosphate (dNTP) molecule that provides the energy for DNA synthesis is the phosphate groups. Nucleotides, including dNTPs, contain one or more phosphate groups, a pentose sugar (in the case of dNTPs, it is deoxyribose), and a nitrogenous base. The phosphate groups in dNTPs release energy when they are cleaved off during DNA synthesis to form phosphodiester bonds between nucleotides.