BIOL 2104 Chapter Notes - Chapter 4: X-Ray Crystallography, Francis Crick, Stem-Loop
19 Dec 2015
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3 specify no codon (amino acid), these are nonsense (stop) codons and serve as termination codons. Aug is initiation codon (specifies met), sometimes gug. Code is unambiguous each codon specifies one amino acid. Code is degenerate except for met and trp, every amino acid coded by more than one codon (codons for same aminoacid are called synonymous) Codons representing the same amino acid or chemically similar amino acid tend to be similar in sequence third-base degeneracy changes in position 1 tend to specify similar a. a. Genetic code is universal (mostlythere are small differences in the genetic codes of single cell ciliates and mitochondria) Francis crick, 1955: reasoned adapter molecules must bridge information gap between nucleic acids (mrnas) and amino acids. Stem loop trna structure base pairing occurs x-ray crystallography and nmr have been used to view the trna in 3d. Correct amino acid must be selected for covalent attachment to a trna by aminoacyl-trna synthetase.
