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.
On a single strand of DNA the nucleotides are held together by covalent bonding between the phosphate group bonded to the 5' end of the deoxyribose, which bonds to another deo â¦ xyribose molecule attached to the next nucleotide on the strand at the 3' end of the sugar. This is what holds together a single strand. When two strands of DNA that have exactly complementary base pairing (Adenine bonds with only Thymine, and Cytosine with Guanine) the base forms a hydrogen bond to the base on the opposite strand, only if the base pairing is complementary.