Biology 97 Lecture 13 Class Notes
Biology 97 Lecture 13 Class Notes 61860
Irvine Valley College
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This 3 page Class Notes was uploaded by Idda Colcol on Tuesday October 4, 2016. The Class Notes belongs to 61860 at Irvine Valley College taught by Amy McWhorter in Fall 2016. Since its upload, it has received 4 views. For similar materials see Genetics and Evolutionary Biology in Biology at Irvine Valley College.
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Date Created: 10/04/16
Bio 97 (#61860): Lecture 13 Class Notes 10/3/2016 (Powerpoint slides “Bacterial Genetics I”) I. Bacterial Clones A. once you spread cells out -> get visible colonies B. colonies result of division C. replicate by binary ﬁssion D. genetic clones of one another II. Mutations in Bacteria A. carbon source mutant - inability to grow when particular sugar is sole sugar or carbon source on medium B. sugars 1. carbons, hydrogens, and oxygens in 1:2:1 ratio a) these are usually sugars 2. polysaccharides need to get broken down into simple sugars 3. needs extra membrane proteins to get into cell 4. cell needs to make extra proteins to utilize these carbohydrate sources C. media 1. MM = glucose (minimal medium) 2. MM + ^x carbon = not glucose a) unless it says AND glucose, assume there are no glucose molecules and whatever is listed is sole carbon source 3. RM = glucose / all metabolites a) glucose and usually has all amino acids and nucleotides D. metabolite mutants 1. chemical that cell utilizes in order for cell to grow 2. anything else that cell needs to grow than carbon source 3. prototrophic a) capable of making everything they need so they grow on minimal medium 4. auxotrophic a) one that has mutation in one of these genes that codes enzyme for producing one or more of these amino acids E. essential amino acids 1. amino acids that our cells can not make 2. we need 20 amino acids, we can make 11 but are missing 9 3. bacteria on the other hand makes its own amino acids a) they possess genetic code necessary to produce own metabolites F. drug resistance mutants 1. antibiotics that target different growth pathways 2. mutations allow bacteria to be come resistant to antibiotic III.Carbon Source Mutants A. lacZ enzyme needs to be functional to be able to split lactose in half B. if mutant for lacZ, it can’t split C. this is different situation than metabolite mutants 1. can’t survive if carbon is only carbon source on medium D. need to consider what type of mutant it is IV. Biochemical Pathways: Synthesizing essential metabolites A. cells that have mutants for any of these enzymes have block in pathways B. there may be three different genes, but any one of them will lead to auxotrophic cell for phenylalanine V. Antibiotic Selections: Drug Resistant mutants A. this mutation gives cell a survival advantage VI. Replica Plating A. original plate is master plate B. 1940s, Lederberg couple 1. wife came up with idea for replica plating 2. replica plating occurs when you transfer colonies using piece of velvet 3. because velvet is spiky C. arrow on both second and master plates indicate same spot to maintain consistency D. this helps us analyze genotypic and phenotypic characteristics on colonies of a cell VII.Selection vs Screen A. selection 1. conditions that allow desired genotype to grow B. screen 1. you’re able to examine each colony and analyze various genotypes and phenotypes 2. we are able to distinguish between wild types from mutants a) can distinguish them visibly VIII.creening for Auxotrophs A. Genotypes of colonies 1. 1: ile+, asp-, met+, arg- 2. 2: ile-, asp+, met-, arg+ 3. 3: ile+, asp+, met+, arg+ 4. 4: ile+, asp-, met+, arg+ B. the book will write the genotypes and phenotypes for which a cell is auxotrophic for and not include prototrophic for because that is considered wild type IX. Screening for carbon source mutants A. lac-man+ara+ = 2 B. lac+man-ara+ = 4 C. lac+man+ara- = 6 D. lac-man+ara+ = 3 E. lac-man-ara- = 5 X. 3 Types of unidirectional gene transfer in bacteria A. conjugation 1. interaction enables cytoplasm to be shared 2. between one cell and its neighbor 3. physical tubes that grow between neighboring cells 4. DNA is sent through that tube B. transduction 1. transfer DNA using viruses 2. anchor to cell wall, spit DNA into cell, and turn cell in virus making factory 3. some of new viruses might mis-package bacterial DNA instead of virus DNA 4. virus is just protein shell with genetic code 5. transfer DNA through virus intermediate C. transformation 1. taking DNA from environment 2. DNA has to be competent a) cell has special enzymes and channel proteins at plasma membrane to enable uptake of large macromolecules b) not something all cells can do D. unidirectional - it can only go in direction XI. Conjugation: Gene transfer in E.coli A. Lederberg and Tatum known for identifying mechanism for gene transfer B. have cells prototrophic for all 5 of these genes 1. somehow mixing strain A and B allowed these genes to recombine XII.Controls for spontaneous mutation A. cross feeding argument 1. met and bio auxotrophic leak substances out into medium that supports growth of opposite auxotrophic type 2. they are mutants but they are able to feed each other 3. they can provide what the other lacks XIII.-tube experiment A. ﬁlter separates separate sides of u-tube B. ﬁlter contains microscopic pores C. shows that there was no growth on MM and that growth needed to occur when both strains were mixed XIV.Genes are transferred in one direction A. physical contact is conjugation B. cells have extensions 1. donor, F+, fertile cell C. cell without extensions 1. recipient, F- D. extensions are called pili 1. make contact with only F- cells 2. start to draw F- cell closer 3. allow for conjugation bridge which is a little tunnel that is surrounded by proteins which allows for cytoplasmic regions of cells temporarily 4. exchange genetic information 5. F plasmid is what is exchanged a) contain bacterial chromosome and fertility, F+ plasmid (1) fertility plasmid has genes that allow replication XV. Fertility (F) factor and unidirectional conjugation A. genes are found on plasmid B. fertility genes remain in donor cell but also have been replicated in recipient cell C. F+ and F- —-> F+ and F+ 1. donor remains unchanged XVI.The F (fertility) factor A. integration sites B. origin of transfer 1. where replication of whole plasmid is initiated 2. is directional, indicated by arrow XVII.The F Plasmid: Rolling Circle Replication A. plasmid will always break at OriT