Microbiology 201 week 4 notes
Microbiology 201 week 4 notes MICRB 201
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This 2 page Class Notes was uploaded by Grace Spellacy on Saturday January 30, 2016. The Class Notes belongs to MICRB 201 at Pennsylvania State University taught by Dr. Steven Keating in Spring 2016. Since its upload, it has received 38 views. For similar materials see Introductory Microbiology in Microbiology at Pennsylvania State University.
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Date Created: 01/30/16
Microbiology 201 WEEK 4 NOTES 2/1/16 Effects of Mutations continued 3. Mutation in the regulatory sequences at the start of genes o Regulatory sequences Determine if the gene will be used Include “promoters” and “operators”’ NOT transcribed o Possible results of a mutation Reduction/ elimination of transcription Transcription depends on binding of RNA polymerase which depends on the DNA base sequence If a mutation changes the DNA base sequence, binding may not occur May result in little or no gene product Result of the cell depends on the protein Unregulated gene expression Normally, Regulation genes could turn off, stopping transcription After a mutation, a change could occur so that a gene is always turned on Can occur if regulatory proteins can’t bind to DNA We may deliberately mutate a microbe for valuable product (ex. Penicillin) Specific types of changes in DNA sequences 1. Base substitution: changing one base pair for another o Common structures Purine for purine: A and G (similar shape) Pyrimidine for pyrimidine: C and T (similar shape) o Many chemicals can cause base substitutions (mutagens) Nucleotide analogs Mimic the shape of a nucleotide May replace a nucleotide by mistake Example: bromo uracilthymine analog Can form a pair with A and G Net result: changes an AT pair to a GC pair o Base substitution and antibiotic resistance Example: resistance to macrolides (erythromycin, azithromycin) by microbacterium avium Can cause a TB like lung infection in immune suppressed people Binds to 23 SrRNA of 50s subunit of prokaryotic ribosome Several mutant strains of microbacterium avium have mutations in DNA for 23 SrRNA Change in DNA from T to A,C or G Change in rRNA from A to U, C, or G Results in changes in shape of rRNA which reduces affinity and raises the dose of antibiotic needed But higher dose leads to more side effects 2. Base deletion and insertion mutation (frameshift) o One base pair is lost or added, which results in shifting the frame around a codon As a result, translation of mRNA begins one base early or late Results in changes of a lot of codons and a lot of amino acids Produces bigger changes than base substitution o Depending on location, can completely destroy protein function o May create novel proteins and new metabolic pathways Example: flavobacterium Flavobacterium gained the ability to use nylon subunits for energy as a result of a frameshift mutation Nylon was invented in the 1930s Nylonase was a result of the mutation which breaks nylon into useful subunits o Chemicals can cause frameshifts Common examples benzpyrene (In car exhaust and cigs) aflatoxins produced by a fungus called aspergillus flavis grows on peanuts flat/ planar shape allows it to intercalate between stacks of bases resulting in frameshifts
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