BIMM 120 – WEEK 5 11/02/20 Sections A03 and A04 IA: Jaxon Wagner ([email protected]) QUIZ 2 CLASS STATISTICS LECTURE 8 REVIEW! J Ø Lecture 8 part II o Horizontal Gene Transfer o Transformation o Transduction o Conjugation Ø Homework o Have Homework Grade by Tomorrow Ø Election Tomorrow! o https://www.sos.ca.gov/elections/polling-place GENE EVOLUTION HOMOLOGOUS RECOMBINATION BY RECA Splices Patches Does not cause complete Causes complete integration of new integration of new DNA! DNA! (Single or Double crossover) HORIZONTAL GENE TRANSFER (HGT) Vertical transfer of genetic material from parent to offspring Horizontal transfer of genetic material Chinmay Kalluraya Significance of HGT in Nature Dr. Lynn Margulis Endosymbiotic Theory Reference: Andrew Z. Colvin - Barth F. Smets, Ph.D. HORIZONTAL GENE TRANSFER • Movement of genetic material other than by parents to offspring. • HGT established method for bacterial evolution. • Mechanisms : transformation transduction conjugation Reference: https://courses.lumenlearning.com/microbiology/ TRANSFORMATION – PLASMIDS • Competent cells can take up external DNA • DNA can be either be integrated into the chromosome via RecA recombinase, or can stay and replicate independently as a plasmid • Plasmids usually do not encode for their own integration • Most plasmids do not get integrated or recombined at all (they stay as plasmids) • If they are integrated, this is usually done by RecA, which is on the chromosome TRANSDUCTION – LYTIC AND LYSOGENIC PHAGES Infection & Injection Some signals (like UV stress) cause Phage DNA to excise from chromosome Lytic Cycle Lysogenic Cycle (All phages) (Only lysogenic phages) Circulization of phage DNA Phage DNA replicates with cell Cell lyses, releasing virions (getting a free ride!) Integration of phage DNA Host chromosome is degraded and phage into chromosome (prophage) DNA is packaged into new virions GENERALIZED TRANSDUCTION USING THE LYTIC CYCLE AND HOPING YOU GET LUCKY (RANDOM) Infection & Injection Circulization of phage DNA Host chromosome degraded, DNA is packaged randomly, phage DNA replicated, some only get host DNA (white) phage parts assembled Cell lyses, releasing virions Infection & Injection Bacterial DNA from another cell is recombined SPECIALIZED TRANSDUCTION LYSOGENIC PHAGES SPECIFICALLY GRAB DNA NEAR THE PROPHAGE Integration of phage DNA Circulization of phage DNA Phage DNA is packaged into new virions Infection & Injection into chromosome (prophage, blue) – some phage DNA has (into new host) near gene of interest (fuschia) Gene Fuschia (%that have Gene Fuschia ~ linkage strength) Linkage: How close your prophage is to your gene of interest Closer (fewer base pairs between) = tighter linkage = higher % of new phage particles that have the gene of interest (can be up to nearly 100%!) CONJUGATION – SEX PILUS AND F- PLASMIDS • Transfer of a conjugation plasmid (F-plasmid) via sex pilus • F-plasmids contain a conjugation sequence and tra genes for pili formation • F-plasmids often encode virulence factors or antibiotic resistances • Plasmids transferred by conjugation can either be replicated as a plasmid or integrated into the new host chromosome via RecA • Don’t sweat the details J.