Other than b and c differ from each other and c

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other than B and C differ from each other, and C differs from A more than B differs from A iv. When do variants become species? 1. Darwin’s time: when the variants are separated long enough and experts agree 2. Today: when the variants don’t breed and exchange genes anymore a. i.e rats and mice don’t exchange genes anymore v. Darwin’s 2 concepts: 1. Common Descent: a. Variation leads to speciation by natural selection b. All species came from a species in the past 2. Natural Selection:
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a. Is the mechanism for gradual change Lecture 4: October 1, 2010 Bacterial Cytoskeleton 1. Preconceptions: a. Eukaryotes are complex organisms i. Nucleus ii. Compartments iii. Cytoskeleton 1. actin 2. tubulin 3. intermediate filaments b. prokaryotes are simple organisms i. Bag of enzymes 2. BUT this isn’t true, prokaryotes also have a cytoskeleton!! a. Alignment of eukaryotic highly conserved 5 sequence motifs to prokaryotic 5 sequence motifs in each protein family: i. Actin ( muscle and cytoskeletal proteins) ii. Hsp 70 ( heat shock proteins) iii. MreB, FtsZ ( prokaryotic cell cycle protein) iv. Etc. b. Found that the relative positions of all the motifs are identical in all of the families, and the distances between the motifs are similar i. Protein Structure is almost always more conserved than DNA sequence/ amino acid sequence ii. this shows that that highly conserved motifs of the proteins present in the eukaryote are similar/ identical to prokaryotes iii. even though plasmid actins are divergent in amino acid sequence, they have a structure similar to eukaryote actin 3. The structure of MreB ( bacterial actin like protein) is very similar to F actin in eukaryotes a. MreB is able to assemble polymers similar to eukaryotic actin b. The polymers contain a protofilament that is very similar to actin 4. Actin like filaments a. Fxn: to maintain the shape of cell b. i.e rod shaped bacteria need actin like proteins to maintain their shape i. they form helical shape down the length of the bacteria underneath the membrane, and it interacts with the peptidoglycan to form the rod shape ii. MreB coordinated peptidoglycan biosynthesis iii. KO MreB the rod shaped bacteria lose their rod shape and lyse 5. Many Alps ( Actin Like Proteins) are encoded by Plasmids( circular DNA in bacteria) = Non essential DNA a. They are self-replicating
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b. Large or small c. They perform a useful fxn i. Plasmids fluid/mobile genome, can be transferred from one bacteria to the next ii. Ex. Bacillus thuringiensis: contains the BT toxin this toxin is produced in this bacteria because of the plasmid it contains 1. Different plasmids can encode for different proteins and toxins in the same bacteria the same bacteria can contain different plasmids and therefore produce different toxins iii. Ex. Bacillus anthracis the bacteria that contains the anthrax toxin 1. pXO1 is the plasmid for the toxin 2.
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