CAS BI 108 Study Guide - Midterm Guide: Aminoacyl Trna Synthetase, Aminoacyl-Trna, Start Codon
29 Feb 2016
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How does information flow from genes to proteins? : chemical structure of nucleic acids, complementary base pairing: Pyrimidines (have one ring): cytosine (c), thymine (t) (in dna), uracil (u) (in rna) Purines (have two rings): adenine (a), guanine (g) (in dna) Pairs are held together with hydrogen bonds: thymine with adenine, cytosine with guanine, anti-parallel: = phosphate group: -- 5" carbon ------------------------------------- 3" carbon. This allows dna polymerase to do its work, adding nucleotides in the 5" 3" direction. Dna polymerase: uses dntps (deoxyribonucleoside triphosphates) as substrates, forming covalent bonds between dntp and the 3" end of the growing polynucleotide chain. In e. coli, the dna helicase is shaped like a donut. The lagging strand is surrounded by helicase, and the leading strand is peeled off: dna topoisomerase removes the knots in the separated dna single strands. Ssbp (single stranded binding protein) protects the strands from degradation: clamp-loader unloads and loads clamps at certain sites along the dna.
