DNA & RNA

• Purine nitrogenous bases are a pyrimidine ring fused with an imidazole ring: adenine and guanine.
• A phosphodiester bond is formed when two ester bonds are formed from each phosphate group.
• Nucleic acids are polymers made of monomers called nucleotides.
• Nucleotides are made of a pentose sugar, a phosphate group, and a nitrogenous base.
• There are 4 nitrogenous bases: guanine, thymine, adenine, and cytosine.
• Nucleotides are made with two condensation reactions: sugar and phosphate are joined by an ester bond, and sugar and the base are bonded by a glycosidic bond.
• Pyrimidine nitrogenous bases are an organic ring of 6 atoms, including 4 carbons and 2 nitrogens: thymine, cytosine, and uracil.
• Polynucleotides are made from many nucleotides, with the phosphate group on carbon 5 bonded to a sugar on its carbon 3 to form a dinucleotide.
• Hydrogen bonds form between nitrogenous bases, with 3 hydrogen bonds between cytosine and guanine and 2 hydrogen bonds between adenine and thymine.
• DNA is strong due to multiple hydrogen bonds and a sugar-phosphate backbone, it contains lots of genetic information, it is helical and compact, and its base sequence codes for amino acids.
• In RNA, thymine is replaced by uracil, and RNA transfers genetic information from DNA to ribosomes.
• Ribosomes are made from RNA and proteins, and RNA is always a single strand.