DNA stands for deoxyribonucleic acid. It is composed of a 5-carbon sugar called deoxyribose, and nucleic acid. Its a nucleotide which means it consists of a sugar molecule attached to a nitrogen base and a phosphate group
DNA has a specific rule of how the nitrogen bases bond. Adenine goes with thymine, and guanine goes with cytosine. There is no other way. These are connected by hydrogen bonds, the weakest most unstable bond there is. There is two different structures, Purines(adenine and guanine) and Pyrimidines(thymine and cytosine). They always pair together. G and C have three hydrogen bonds, while A and T have only 2.
DNA is in a double helix shape,(like a twisted lader) which is coiled up to save room. The sugar part (phosphate) is the back bone part, and the nitrogen bases are the rungs
Replication of DNA requires it to "unzip" and then expose its nucleotides. Then DNA polymerase determines what the other half of the ladder is based on the original copy. Because DNA is so long, it happens at multiple parts of the strand simultaneously.