If you do not have an SSN and are not eligible to obtain an SSN, but you have a requirement to furnish a federal tax identification number or file a federal income tax return, you must apply for an ITIN. By law, an alien individual cannot have both an ITIN and an SSN.
DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix.
Nucleic Acids. The structure of DNA consists of two strands of nucleotides that are paired together to form a ladder-like structure. One strand of DNA is the template from which the other one is built. The nitrogenous bases of each nucleotide pair together in specific combinations in order to form the structure of DNA. Each rung of the ladder is a pairing of nitrogenous bases. The types of nitrogenous bases that make up RNA and DNA molecules: