November 11

Notes November 11, 2009 Lectures

B. Codon- three bases long sequence on the messenger RNA that corresponds to a particular amino acid
- 20 aa; 64 possible codons
- Ch. 8 in big txt. Read
1) Redundant codons: > 1 codon per amino acid
C. Messenger RNA
- single stranded
- transcribed off of DNA
1st step in translation to protein:
i) Ribosome is going to have to attach to mRNA and the Shine- Dalgarno sequence
a. Shine Dalgarno- specific series of bases on the messenger RNA that are complimentary to sequence of bases in rRNA
D. after attaching to the shinedelgarno sequence the rRNA is going to move down the mRNA one bases at a time until it reaches the start codon of AUG- begins translating
- initial AUG codon is going to define the reading frame for the rest of the mRNA
- every three bases following the AUG are translated
E. tRNA- transfer RNA anticodon on one side complimentary to each codon, and an amino acid on the other ; rRNA brings in tRNAs and matches them with codons on mRNA
- amino acid attached to tRNA that attaches to AUG is Met
- table relates the mRNA codon and the aa

F. Ribosome is going to catalyze the bond between the two amino acids that are adjacent to each other hooking them together- tRNA detached from amino acid
- keeps going until reaching the Stop codon that is going to drop the amino acid DNA bc there is no transfer RNA that has an anticodon that corresponds to the stop codons of UAA, UAG, UGA
G. bc there is no tRNA that is complimentary to a stop codon when the ribosome reaches the stop codon it can’t base pair any tRNA , aa in there
- rRNA pauses at stop codon – proteins called release factors
Release factors interact with stop codon instead- bing w/ stop codons, catalyze release og amino acid chain from ribosome and ribosome from mRNA

Clostridium perfringens- gram + bacteria that live in the soil are strict anaerobes that cannot grow in the presence of oxygen
- Can make spores
Spores- hardy, sturdy nonmetabolic state that some gram + bacteria can enter into
- Spore is locted in the hollow
- Common soil bacteria in US and around Europe
- Specific sigma factors that bacteria express in the presence of oxygen so they may live in the presence of oxygen- spore genes are turned on by the expression of the specific sigma factors ( spore genes are not turned on all the time)
- Spore- gene sigma factor in high 02 and low h20

• When actively growin CP has a virulence factor called phospholipase (enzyme that breaks down phospholipids) – when men in ww1 were living in trenches their boots stayed on for months creating an anaerobic environment w/ CP in the mud- virulence factor created massive blisters on the food bc the phospholipase is being produced
• Under the layers of dead tissue is anaerobic conditions which are great growing situations for CP spores that start to grow into active bacteria

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