1. CHAPTER 18 MICROBIAL MODELS: THE GENETICS OF VIRUSES AND BACTERIA

2. I. THE GENETICS OF VIRUSES A. RESEARCHERS DISCOVERED VIRUSES BY STUDYING A PLANT DISEASE: SCIENCE AS A PROCESS IN THE LATE 1800S SCIENTISTS FOUND AN INFECTIOUS AGENT MUCH SMALLER THAN BACTERIA

4. B. A VIRUS IS A GENOME ENCLOSED IN A PROTECTIVE COAT. A VIRUS IS A SMALL NUCLEIC ACID GENOME ENCLOSED IN A PROTEIN CAPSID AND SOMETIMES A MEMBRANOUS ENVELOPE. THE GENOME MAY BE SINGLE OR DOUBLE STRANDED DNA OR RNA

6. C. VIRUSES CAN REPRODUCE ONLY WITHIN A HOST CELL: AN OVERVIEW VIRUSES USE ENZYMES, RIBOSOMES, AND SMALL MOLECULES OF HOST CELLS TO SYNTHSIZE PROGENY VIRUSES. EACH TYPE OF VIRUS HAS A CHARACTERISTIC HOST RANGE, DETERMINED BY SPECIFIC RECEPTORS ON HOST CELLS

7. A SIMPLIFIED VIRAL REPRODUCTIVE CYCLE

8. D. PHAGES REPRODUCE USING LYTIC OR LYSOGENIC CYCLES IN THE LYTIC CYCLE, INJECTION OF A PHAGE GENOME INTO A BACTERIUM PROGRAMS DESTRUCTION OF HOST DNA, PRODUCTION OF NEW PHAGES AND DIGESTION OF THE HOST’S CELL WALL, RELEASING THE PROGENY PHAGES. IN A LYSOGENIC CYCLE, A TEMPERATE PHAGE INSERTS ITS GENOME INTO THE BACTERIAL CHROMOSMOE AS A PROPHAGE, WHICH IS PASSED ON TO HOST DAUGHTER CELLS UNTIL IT IS STIMULATED TO LEAVE THE CHROMOSOME AND INITIATE A LYTIC CYCLE.

9. THE LYTIC CYCLE

11. II. THE GENETICS OF BACTERIA A. THE SHORT GENERATION SPAN OF BACTERIA FACILITATES THEIR EVOLUTIONARY ADAPTATION TO CHANGING ENVIRONMENTS THE BACTERIAL CHROMOSOME IS A CIRCULAR DNA MOLECULE WITH FEW ASSOCIATED PROTEINS PLASMIDS ARE SMALLER RINGS OF DNA WITH ACCESSORY GENES. BECAUSE BACTERIA PROLIFERATE RAPIDLY AND HAVE A SHORT GENERATION SPAN, NEW MUTATIONS CAN AGGECT A POPULATION’S GENETIC VARIATION QUICKLY

12. REPLICATION OF BACTERIAL CHROMOSOME

13. B. GENETIC RECOMBINATION PRODUCES NEW BACTERIAL STRAINS THE MECHANISMS OF GENE TRANSFER BETWEEN BACTERIA ARE TRANSFORMATION, TRANSDUCTION, AND CONJUGATION. IN TRANSFORMATION, NAKED DNA ENTERS THE CELL FROM THE SORROUNDINGS IN TRANSDUCTION, BACTERIAL DNA IS CARRIED FROM ONE CELL TO ANOTHER BY PHAGES IN CONJUGATION, AN F-FACTOR CONTAINING “MALE” CELL TRANSFERS DNA TO AN F- CELL. (BACTERIAL SEX)

14. DETECTING GENETIC RECOMBINATION IN BACTERIA