DNA replication is semi-conservative and involves several key enzymes. DNA helicase unwinds and unzips the parental DNA, then RNA primase adds short RNA primers to each strand. DNA polymerase adds complementary nucleotides to each new strand in the 5' to 3' direction, with the leading strand synthesized continuously and the lagging strand synthesized discontinuously in fragments called Okazaki fragments. DNA ligase joins the Okazaki fragments together. The end result is two double-stranded DNA molecules that each contain one old and one new strand.
Tetracyclines are a class of broad-spectrum antibiotic drugs obtained from Streptomyces bacteria. They work by inhibiting bacterial protein synthesis. Resistance can occur via efflux pumps, ribosomal protection, or enzymatic oxidation. Tetracyclines have a general structure of a four-ring hydrocarbon system. Derivatives include doxycycline, minocycline, and tigecycline. They are used to treat infections from bacteria, protozoa, and rickettsiae. Adverse effects include gastrointestinal issues and tooth/bone staining.
