Explanation:

Antiparallel DNA strands refer to the way in which the two strands of DNA run in opposite directions. The 5' end of one strand is paired with the 3' end of the other strand. This is due to the way in which the nucleotides are connected to form the DNA strands.

H-bonds:
Hydrogen bonding between the nitrogenous bases (A-T and G-C) holds the two strands of DNA together. This bonding occurs between the complementary base pairs, with A always pairing with T and G always pairing with C. These base pairs are held together by hydrogen bonds, which are relatively weak interactions.

Phosphodiester bonds:
Phosphodiester bonds connect adjacent nucleotides within a single strand of DNA. These bonds form between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of the adjacent nucleotide. This results in a sugar-phosphate backbone that runs along the length of each DNA strand.

Antiparallel orientation:
The antiparallel orientation of DNA strands is a result of the way in which the nucleotides are connected by phosphodiester bonds. The 5' end of one strand is always paired with the 3' end of the other strand, resulting in an antiparallel orientation.

Conclusion:
In conclusion, the antiparallel orientation of DNA strands is due to the way in which the nucleotides are connected by phosphodiester bonds. Complementary base pairing between the nitrogenous bases is held together by hydrogen bonds.

The nucleic acid sequences are complementary and parallel, but they go in opposite directions, hence the antiparallel designation. The antiparallel structure of DNA is important in DNA replication because it replicates the leading strand one way and the lagging strand the other way.

-A DNA molecule consists of two strands of nucleotides twisted together to form a double helix. The sugar-phosphate backbone is found on the outside of this helix and the bases are found braching towards the middle. Hydrogen bonds join the the nitrogenous bases and hold the two strands together.