Describe the structure of nucleic acids, making reference to how nucleotides are joined and to how DNA strands are joined together. Describe the three types of RNA and their functions, comparing the structure of RNA to that of DNA.
Linked by bonds that form between the phosphate group and sugar of successive nucleotides, nucleic acid nucleotides are arranged in long chains with their nitrogenous bases oriented as side groups off the main chain. It is the sequence of nucleotides that encodes hereditary information as well as provides the information for the sequencing of amino acids in protein synthesis. DNA molecules are composed of two nucleotide chains oriented in opposite directions and held together by hydrogen bonds between adjacent bases. This double chain is coiled into a double helix, a form that imposes constraints on which bases can bond with each other. Thus, only two types of pairings are possible: adenine to thymine and guanine to cytosine. Yet any order of these pairings is possible, and, thus, DNA can have four possible cross-rungs (adenine-thymine, thymine-adenine, guanine-cytosine, and cytosine-guanine). There are three types of RNA: 1) messenger RNA (mRNA) carries instructions from the DNA in the nucleus to the sites of protein synthesis in the cytoplasm, 2) ribosomal RNA (rRNA) is a structural component of these protein synthesis sites, called ribosomes, and 3) transfer RNA (tRNA) brings amino acids into the ribosomes so that they can be
