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Micro. Lect. Notes Weeks 4 & 5

by: Madi Burke

Micro. Lect. Notes Weeks 4 & 5 BIOL 2051

Madi Burke

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About this Document

Notes from weeks 4 & 5 of class, covers material discussed from the Genetics unit
Prof. Brininstool
Class Notes
Microbiology, micro, Biology, Science, Genetics
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This 4 page Class Notes was uploaded by Madi Burke on Saturday September 24, 2016. The Class Notes belongs to BIOL 2051 at Louisiana State University taught by Prof. Brininstool in Fall 2016. Since its upload, it has received 27 views. For similar materials see Microbiology in Biological Sciences at Louisiana State University.


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Date Created: 09/24/16
th Wednesday, September 14 , 2016 Central Dogma: DNA -> RNA -> Protein ~ Replication: copying ~ Transcription: DNA -> RNA ~ Translation: RNA -> protein (A.A’s) *Making of informational macromolecules for the cell* Eukaryotes have linear chromosomes, but some viral chromosomes can be linear as well (viral advantage, replicating mechanisms of the host). DNA Structure: 2 anti parallel strands, complementary sequencing, hydrogen bonds Adenine & Thymine ( 2 bonds ) Guanine & Cytosine ( 3 bonds ) Bacteria supercoil their DNA. Eukarya form nucleosomes using histones. Archaea can have either. RNA Types: messenger, transfer, ribosomal ~ Messenger RNA or mRNA = what is translated into proteins ~ Transfer RNA or tRNA = carries A.A.’s to put into proteins (tRNA complex?) ~ Ribosomal RNA or rRNA = puts mRNA & tRNA together for the synthesis of proteins Transcription: ~ promoter region = a sequence of DNA before the start site of transcription ~ transcription start site = a nucleotide on the DNA where RNA-polymerase starts transcribing ~ RNA-polymerase = compliments the DNA template with ribonucleotides, forms one RNA molecule 1: rRNA 2: mRNA 3: tRNA ~ terminator region = DNA sequence signaling the end of transcription Eukaryotes transcribe a single gene at a time. They also have introns (non-coding DNA) and exons (coding DNA). A transcription factor help RNA polymerase bind to the promoter region (Remember: there is no sigma factor in Eukaryotes). In bacteria, there is a single RNA-polymerase with a sigma factor attached. This sigma factor bind to a promoter region and the RnA-polymerase starts transcribing. In prokaryotes, there are no introns, right? So that means multiple genes can be transcribed at a time. This forms polycistronic mRNA. Transcription Termination: ~ Rho-dependent = (Ecoli protein = name) binds to RNA when moving into the polymerase complex; triggers release of RNA-polymerase when Rho-dep. Terminating site is reached ^ only in Bacteria ~ Intrinsic = extra proteins; inverted repeats form a loop that results in termination *See chart from slide 23* Operons = several genes can be transcribed at the same time; they encode rRNA or proteins to be used together(only found in Eukaryotes in mitochondrial and chloroplast genomes) Regulating Transcription: ~ Bacteria & Archaea = similar ~ Eukarya = extra regulations/controls Ex: repressor + activator (proteins); 2 comp. system; multi-comp. system (“phosphorelay transfer”) *Negative Control: transcription prevention, … Ø Enzyme repression = # of product halts synthesis of enzymes be they aren't needed The operator is where enzyme repressing proteins bind. Ex: arginine present = binds to repressor = binds to operator = transcription ^ “co-repressor” Ø Enzyme induction = # of substrate encourages enzyme synthesis to use substrate *Positive Control: - activating transcription - activator protein binds when inducers present Ø Catabolite repression = Catabolite replaces protein in repression o “Glucose effect” = efficient b/c goes straight to glycolysis o “Diauxic growth” *Throwback to Biology 1201: cyclic AMP* Happens in the absence of glucose (only). See fig. 7.15 Ex: lac & mal = slides 36-41 Regulons = when many operons are controlled by a single regulatory protein See Slide 43 for transcription control in Archaea. In a 2 component regulatory system, sensor kinase auto-phosphorylates when it receives a signal from the environment (receptor protein). The phospohyl group is transferred to a response regulator, which can bind to DNA, affecting transcription. (In slide 44, the response regulator is a repressor protein.) In a multi-component transfer system, external signals trigger phosphorylation of the sensor kinases. These external signals can be things from the environment such as desiccation, starvation, or changes in cell density. (See slides 45 & 46 for detailed visual.) A sigma factor is involves. This system regulates sporulation (endospore formation). Translation: ~ mRNA translated to proteins (A.A.’s) ~ need mRNA, tRNA, & ribosomes (rRNA + proteins) Note: In translation, GTP is required. Aka: translation is energetically expensive! {Initiation, Elongation, Termination} Codons: 3 nucleotides next to each other in a sequence of mRNA ~ start = AUG (aka: where translation starts) • bacteria = N-formylmethionine (f-Met) • archaea & eukarya = methionine (Met) ~ stop = UAA, UAG, UGA (aka: where translation stops) Ø opening reading frame = start codon -> stop codon Genetic Code = mRNA codons, many codons can code for one kind of amino acid tRNA is attached to the A.A. that goes with the particular codon; anticodons temporarily match with mRNA codons during translation. Ribosomes: ~ mRNA + aminoactyle tRNAs = protein synthesis ~ start codon -> stop codon ~ moves one codon at a time along mRNA molecule Polysomes = several ribosomes translating 1 mRNA molecule at once ^ because ribosomes are pretty big, they attach only to sites that are 35 nucleotides away from each other Ionizing radiation: ~ goes through tissues, forms ions that can break covalent bonds ~ Low levels = point mutations ~ High levels = chromosomal mutations ~ Cumulative doses of radiation ~ Ex: x-rays, cosmic rays, radons Intercalating agents: ~ Ex: ethicist bromide ~ relaxes helix when inserted into one or both strands (between bases) ~ if the strand gets replication, there will be an extra base inserted The Ames Test: his- salmonella cannot make histidine so it needs to eat it Insertion / Deletion Effects: frame shifts Friday, September 23 , 2016 Transposable Elements: (aka: mobile elements) ~ DNA that can move around in the genome ~ mutation by insertion ~ prokaryotic & eukaryotic ~ 2 kinds: è autonomous = self-transposable, inserts to cause unstable allele è nonautonomous = not self-transposable, lacks the transposase gene, stable insertions, needs autonomous to move around ~ consequences: o loss of function mutation (null mutation) o altered gene expression o common = deletions & insertions ~ classes: Ø move as DNA {Bactrian insertion sequence (IS) & transposons (Tn) § IS1 & IS2, etc. § 768-5000 base pairs in length § Ended by inverted repeats § Transposase gene codes for transposase enzyme (cuts DNA & moves it) § Jagged / “sticky end” cut ~~~~~~~~~~~~~~~~~~~~~ § 2 kinds of transposons • Composite = (Tn10) antibiotic resistant genes, conservative, IS elements at the ends • Noncomposite = (Tn3) antibiotic resistant genes, transposase gene, replicative, IS Ø Transposons in Yeast (Ty elements) (retrotransposons) § TyA = gag structural protein § TyB = pol polyprotein § Retrovirus progenitors Mutation Rates ( see slide 80 ) ~ Note: mutated DNA can be repaired ( see slide 81 )


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