november 11 notes

November 11, 2009—notes
Overview of translation:
1) DNA gene—mRNA transcript—- amino acid chain
2) Codon: 3 mRNA nucleotide sequence that codes for specific amino acids
a) Redundant codons: more than one codon per amino acid
3) Ribosome binds to mRNA: at the Shine-Dalgarno sequence ( a specific series of bases on mRNA that are complementary to sequence of bases in rRNA)
4) AUG= start codon; also methionine
a) Ribosome moves 1 base at a time down mRNA until it reaches AUG- this defines “Reading Frame” of mRNA
5) tRNA: cloverleaf- shaped with anticodon on one side, and amino acid on the other
a) rRNA brings in tRNAs and matches them with codons on mRNA
6) at amino acids linked into a chain by ribosome
a) rRNA forms bond between amino acids that are adjacent to each other—tRNA detached from amino acid
7) at stop codon (UAA, UAG, or UGA) ribosome releases mRNA and amino acid chain
a) because no tRNA with anticodon complementary to stop codons , rRNA pauses at stop codon—proteins called Release Factors bind with stop codons, catalyze release of amino acids of amino acid chain from ribosome, and ribosome from mRNA
A story about gene expression and Armistice Day—handout
1) clostridium perfringes
a) soil bacterium
b) strict anaerobe
c) spore-forming
• very sturdy, non-metabolic state some gram positive bacteria can enter
• gene sigma factors in high [O2], low[H2O]
2) virulence factors
a) exotoxins
• phospolipase

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