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+ Bacterial Genetics March 2015

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+ Terminology Genetics: The study of what genes are, how they carry information, how information is expressed, and how genes are replicated Gene: A segment of DNA that encodes a functional product, usually a protein Chromosome: Structure containing DNA that physically carries hereditary information; the chromosomes contain the genes Genome: All the genetic information in a cell Plasmid small circular DNA molecule that replicates independently of the chromosome

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+ Figure 8.3b DNA Polymer of nucleotides: Adenine, thymine, cytosine, and guanine Double helix associated with proteins "Backbone" is deoxyribose-phosphate Strands are held together by hydrogen bonds between AT and CG Strands are antiparallel

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+ Figure 8.5 DNA Synthesis

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+ Figure 8.6 Replication of Bacterial DNA

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+ Transcription DNA is transcribed to make RNA (mRNA, tRNA, and rRNA) Transcription begins when RNA polymerase binds to the promoter sequence Transcription proceeds in the 5' 3' direction Transcription stops when it reaches the terminator sequence

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+ Figure 8.7 The Process of Transcription

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+ Figure 8.2 Translation mRNA is translated in codons (three nucleotides) Translation of mRNA begins at the start codon: AUG Translation ends at nonsense codons: UAA, UAG, UGA

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+ Figure 8.10 Simultaneous Transcription & Translation

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+ Figure 8.24 Genetic Transformation Frederick Griffith (1920s)

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+ Recombinant DNA Technology Recombinant DNA: DNA made from two different sources. In the 1960s, Paul Berg inserted animal DNA into bacterial DNA, and the bacteria produced an animal protein

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+ Recombinant DNA Technology 1941: George Beadle and Edward Tatum showed that genes encode a cells enzymes 1944: Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA was the hereditary material 1961: Francois Jacob and Jacques Monod discovered the role of mRNA in protein synthesis

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+ Figure 8.2 The Flow of Genetic Information

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+ Vertical gene transfer: Occurs during reproduction between generations of cells. Horizontal gene transfer: The transfer of genes between cells of the same generation. Genetic Recombination

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+ Figure 8.25 Genetic Recombination

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+ Transmission of Genetic Material in Bacterial Cells

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+ Conjugation

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+ Transformation

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+ Transduction

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+ 3 main categories of genes Structural genes Code for proteins Regulatory genes Control gene expression RNA coding genes

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+ Operons: The Basic Concept Operator -the regulatory switch, a segment of DNA usually positioned within the promoter Operon (DNA) includes the operator, the promoter, and the genes that they control In coordinate control, a cluster of functionally related genes can be controlled by a single on- off switch

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+ Activator (protein) when stimulated, changes shape and binds to the promoter to increase the affinity of RNA polymerase to the promoter (increasing the rate of transcription). - The lac operon is stimulated by a small organic molecule known as cAMP that is produced in response to low cellular glucose. Operons: Activation

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+ Operon: Lactose Metabolism

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+ Lac Operon: Sensing Glucose vs. Lactose Bacterial will always prefer glucose over lactose if it is available. Thus, how does E. coli sense when glucose levels are low? How does it relay that information to the genome?

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+ Lactose present No glucose Lactose and Glucose present Figure 8.15 Operons: Activation of Lac Operon

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+ Repressor (protein) switches the operon off Prevents transcription by binding to the operator and blocking RNA polymerase the product of a separate regulatory gene can be in an active or inactive form, depending on the presence of other molecules Corepressor cooperates with a repressor protein to switch an operon off Operons: Repression

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+ When a repressor is bound to the operator, RNA poly cannot bind the promoter and transcription is turned off When the repressor is not bound to the operator, RNA poly can bind the promoter and transcription is turned on. Operons: Relieving Repression

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+ Biotechnology Recombinant DNA technology, a new technique for biotechnology, enables bacteria and fungi to produce a variety of proteins including vaccines and enzymes Missing or defective genes in human cells can be replaced in gene therapy Genetically modified bacteria are used to protect crops from insects and from freezing

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Figure 9.11

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+ pGLO Plasmid DNA

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+ Lac Operon vs Ara Operon

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+ Replacing Ara operon with GFP gene

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+ Figure 8.26 Bacterial Conjugation

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+ Plasmids Conjugative plasmid: Carries genes for sex pili and transfer of the plasmid Dissimilation plasmids: Encode enzymes for catabolism of unusual compounds R factors: Encode antibiotic resistance

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+ Figure 8.29 R Factor, a Type of Plasmid

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+ Figure 8.27a Conjugation in E. coli

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+ Figure 8.27b Conjugation in E. coli

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+ Figure 8.28 Transduction by a Bacteriophage