Genetics Notes test 3

Genetics Notes test 3 - Genetics (for test 3) Lecture 1...

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Genetics (for test 3) Lecture 1 – Genetic Mapping A a A gene = hair color B b B gene = eye color C c C gene = height 2 homologous chromosomes A=brown a=blonde B=brown b=blue C=short c=tall Note: Real genes are far more complex than this A is closer to B than to C – important because of recombination and crossing over A would most likely cross over with B I. Bacteriophage (viruses) Reproduction Requires: A. Attachment to outer surface of the cell B. Inject/Insert its genetic material into the cell C. Take over bacteria cellular “machinery” D. Cell becomes a phage “factory” to make new little phages E. Release new phage offspring via cell lyses (breaking of cell apart) All bacteria Phage + Bacteria Plaque – where phage is on the plate
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Multiplicity of infection (MOI) Number of phage/number of bacteria cells Lytic Cycle Only = virulent phage Insert/Inject the genetic material = called lysogeny (lysogenic cycle) a) phage nucleic acid replicates as a plasmid OR b) Integrated into bacteria chromosome Reversible – called induction when it goes back to the lytic cycle Temperate phage = can switch between the lysogenic and the lytic cycle UV rays and heat can cause a phage to switch from lysogenic cycle to the lytic cycle because of stress in the cell. 10% of phages are virulent phages 90% of phages are temperate phages Beta mutant phages don’t infect the same cells as regular WT phages Other mutant phenotypes can be: virulent or temperate how it effects the bacteria RNA T 4 phage – S. Benzer discovered it Worked with the RII mutant WT T 4 plaque RII Mutant plaque
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RII mutant plaques are bigger. conditional lethal mutant (both permissive and restrictive) Permissive conditions: WT T 4 and RII mutant can infect and reproduce in E.coli B bacteria Restrictive conditions: Both can infect, only WT can reproduce in E.coli K (lambda) WT can infect and reproduce in both types of E.coli bacteria RII mutant can only reproduce in E.coli B – it can infect E.coli K (lambda) but it cannot reproduce – the mutant rate is fairly high in RII mutants Ex.)- Found 20,000 mutants after 1 week WT T 4 DNA Mutation site RII96 Mutant DNA X Crossing over site RII23 Mutant DNA X RIIDII Mutant DNA X
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1. In lab, treat cells (with chemicals/detergents etc) this causes them to take up DNA (competent – to take up DNA) : treat cells so they can take plasmid DNA up, and can be used to make partial diploids 2. In “nature”, naturally “competent” bacteria (Griffith Experiment) – naturally competent bacteria have proteins to bring in DNA B. Conjugation – requires the cell to cell contact – SEX! 1. F episome – carries genes for only 2 functions: the ability to make protein structure called the F-pilus (F pilus gene) as well as the ability to transfer a copy of the F episome to another cell.
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A. F episome B. HFr (integrated F episome on chromosome) HFr cell F pilus F- cell integrated F chromosome chromosome HFr cell F pilus
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This note was uploaded on 04/18/2008 for the course BIOL 330 taught by Professor Perlin during the Spring '08 term at University of Louisville.

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Genetics Notes test 3 - Genetics (for test 3) Lecture 1...

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