The two polynucleotide chains in DNA are

DNA (Deoxyribonucleic acid) is a double helix where the nucleotide forms the structural base. The two polynucleotide strands run 'antiparallel' to each other, with nitrogenous bases projecting inwards. The term 'antiparallel' means that the strands run in opposite directions, parallel to one another. The antiparallel strands twist in a complete DNA structure, forming a double helix.