Complex sentence: These nucleotide triphosphates possess a non-canon sugar, dideoxyribose which lacks 3' hydroxyl group (which accepts the phosphate) and therefore cannot bond with the next base, terminating the chain as the DNA polymerases mistake it for a regular deoxyribonucleotide.
Split into simpler sentences: These nucleotide triphosphates possess a non-canonical sugar, dideoxyribose, which lacks the 3'hydroxyl group normally present in DNA and therefore cannot bond with the next base. The lack of the 3' hydroxyl group terminates the chain reaction as the DNA polymerases mistake it for a regular deoxyribonucleotide.