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Unformatted text preview: Microbial Genetics DNA Deoxyribonucleic Acid Double stranded chain of deoxyribose (pentose sugars) separated by phosphate groups and cross-linked by pairs of nitrogenous bases Nitrogenous bases are made up of 2 groups: o Purines Adenine and Guanine o Pyrimidines Thymine and Cytosine A pairs with T and G pairs with C, no exceptions Control the metabolism of all living cells because they control the synthesis of proteins (enzymes the tools used by cells for all cell functions) DNA is essentially blueprints encoded on genes for the assembly of enzymes. 2 stands 5 to 3 (roof of pentose down) and 3 to 5 (roof of pentose up) All living organisms have DNA and/or RNA (viruses only have RNA) Each cell only gets one copy of DNA making it irreplaceable Every cell has some sort of chromosomes Entire genetic language has only 64 words Watson and Crick Built on work of Pauling, Wilkins and Franklin to determine structure of genetic materials. The Semi-Conservative Method of Replication of DNA Each side of the double helix is a mirror image of the other which can be used to replicate the complementary strand. All cells replicate DNA by the semi-conservative replication method, whether it use mitosis, meiosis or fission New cell needs new copy of instruction manual for metabolism 99% of all errors made during DNA replication is lethal to cell 1. DNA helicase (enzyme) unwinds the coiled double helix o Beginning at the replication fork o Uncoils double helix and separate nitrogenous bases by breaking HFON bonds o Unzipping the zipper 2. DNA polymerase (enzyme) separate the complementary DNA strands o Results in one 5 to 3 strand and one 3 to 5 strand o DNA polymerase acts as an assembler o Each separated strand is used as a template for synthesis of a new complementary strand (3 to 5 strand used to replicate a new 5 to 3 strand o DNA polymerase can form chemical bonds between deoxyribose and nitrogenous bases, but also can H bond nitrogenous bases together (cross-link) 3. DNA polymerase assembles new nucleotides by attaching nitrogenous bases to the sugars to build nucleotides o DNA polymerase can attach new nucleotides only in the 5 to 3 direction o Synthesis will proceed in opposite directions along the complementary strands of Exam 2 Study Guide Page 1 DNA o In the end you have 2 identical strands of DNA each with one original or parent strand and one complementary daughter strand cross-linked by complementary nucleotides. o The 5 to 3 strand can be synthesized continuously, but the other strand is synthesized in small fragments discontinuous synthesis o Continuous synthesis means that the backbone is completed and the bases are popped on....
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