Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE Chapter 8, part C Microbial Genetics
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Change in the genetic material Mutations may be neutral, beneficial, or harmful Mutagen: Agent that causes mutations Spontaneous mutations: Occur in the absence of a mutagen Mutation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Base substitution (point mutation) Missense mutation Mutation Figure 8.17a, b Change in one base Result in change in amino acid
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nonsense mutation Mutation Results in a nonsense codon Figure 8.17a, c
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Frameshift mutation Mutation Figure 8.17a, d Insertion or deletion of one or more nucleotide pairs
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone. Nucleotide excision repairs mutations Mutation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings UV radiation causes thymine dimers Light-repair separates thymine dimers Mutation Figure 8.20
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Spontaneous mutation rate = 1 in 10 9 replicated base pairs or 1 in 10 6 replicated genes Mutagens increase to 10 –5 or 10 –3 per replicated gene The Frequency of Mutation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Selection Positive (direct) selection detects mutant cells because they grow or appear different. Negative (indirect) selection detects mutant cells because they do not grow.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Replica Plating Figure 8.21
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The Ames Test for Chemical Carcinogens Figure 8.22
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Vertical gene transfer Horizontal gene transfer Genetic Transfer and Recombination Occurs during reproduction, between generations of cells Transfer of genes between cells of the same generation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Transformation Figure 8.24
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Recombination Figure 8.25
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation Figure 8.27a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation Figure 8.27b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation Figure 8.27c
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Exchange of genes between two DNA molecules Crossing over occurs when two chromosomes break and rejoin Genetic Recombination Figure 8.23
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Transduction Figure 8.28 Recombinant 1 Phage protein coat Bacterial chromosome 2 3 Bacterial DNA Phage DNA 4 Recipient cell 5 Donor bacterial DNA Recipient bacterial DNA Recombinant cell A phage infects the donor bacterial cell. Phage DNA and proteins are made, and the bacterial chromosome is broken down into pieces. Occasionally during phage assembly, pieces of bacterial DNA are packaged in a phage capsid. Then the donor cell lyses and releases phage particles containing bacterial DNA. A phage carrying bacterial DNA infects a new host cell, the recipient cell. Recombinant can occur, producing a recombinant cell with a genotype different from both the donor and recipient cells.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Conjugative plasmidCarries genes for sex pili and transfer of the plasmid Dissimilation plasmids Encode enzymes for catabolism of unusual compounds R factorsEncode antibiotic resistance Plasmids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Plasmids Figure 8.29
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Segments of DNA that can move from one region of DNA to another Contain insertion sequences for cutting and resealing DNA (transposase) Complex transposons carry other genes Transposons Figure 8.30a, b