Chapter #8
MICROBIAL GENETICS:
OVERVIEW:
If we can identify all the genes in an organism, and determine the functions of each, can we explain
all of biological behavior? What genes do organisms have in common, and what genes make them
unique? What genes cause certain microbes to be harmful or even deadly and how can we develop
drugs or techniques that target a pathogen’s genes?
These are the kinds of questions that define genetic research. We now have complete genome
maps, or genetic blueprints, of hundreds of viruses, bacteria, and other organisms. In addition, we
have a working draft of the human genome, which our knowledge of microbial genetics is helping us
to analyze. For example, by studying the genes of Eschericia coli bacterium and then identifying
which genes we share, we can determine the roles these same genes play in humans. Genetically
speaking, humans have much more in common with microorganism than most people think!
OBJECTIVES:
The Structure and Function of Genetic Material:
1. Define the following: genetics, genome, chromosome, gene, genomics.
2. Explain how the genotype of an organism determines its phenotype (note, you must define and
understand genotype verses phenotype).
3. Describe the structure of DNA, and discuss how it facilitates the ability of DNA to act as a
genetic material (note, if you need additional information about the chemical structure of DNA
or the chemical properties of DNA, see chapter 2, section of DNA).
4. Describe the process of DNA replication as a semiconservative process. Note, be sure to
understand this process and the main players (leading strand, lagging strand, DNA
polymerase, RNA primer, etc).
5. Compare and contrast the synthesis of leading and lagging strands of DNA replication (note,
figure 8.4 very helpful for understanding this).
RNA and Protein Synthesis:
6. Explain the central roles of DNA and RNA in polypeptide synthesis.
7. Describe three steps in RNA transcription, mentioning the following: DNA, RNA polymerase,
promoter, 5’ to 3’ direction, and terminator.
8. Differentiate between transcription and translation.
9. Describe the genetic code in general, and identify the relationship between codons and amino
acids.
10. Describe the translation of polypeptides, identify the roles of the three types of RNA. (Note,
figures are very helpful here as well)!
The Regulation of Bacterial Gene Expression:
11. Explain the operon model of transcriptional control in prokaryotes.
12. Contrast the regulation of an inducible operon with that of a repressible operon, and give an
example of each – I suggest a drawing or chart comparing the two.
13. Describe how catabolite repression is used to control gene expression.
Mutation: Change in the Genetic Material:
14. Define mutation.
15. Classify mutations by type, and describe how mutations are prevented and/or repaired.
16. Define mutagen.
17. Describe at least two kinds of chemical mutagens and their effects.
18. Discuss how different types of radiation cause mutations in a genome.
19. Describe two ways mutations can be repaired.
20. Describe the relative frequency of deleterious and useful mutations and their effect on the
mutation rate.
21. Contrast the positive and negative selection techniques for isolating mutants.
22. Briefly describe the Ames test- what typing of testing is it commonly used for – ie what does it
help identify.
Genetic Recombination and Transfer:
23. Define genetic recombination.
24. Identify the mechanisms of genetic recombination in bacteria.
25. Which of the following is used by bacteria to transfer genetic information from parent to
offspring - vertical gene transfer or horizontal gene transfer – explain your answer.
26. Explain the roles of F factor, F+ cells, and Hfr cells in bacterial conjugation.
27. Compare and contrast crossing over, transformation, transduction, and conjugation.
28. Describe the structures and actions of simple and complex transposons.
Genes and Evolution:
29. Discuss how genetic mutation and recombination provide material for natural selection to act
upon.
SUPPLEMENTAL SITES:
 Great Interactive Transcription/Translation Site which allows you to participate in both
processes: http://learn.genetics.utah.edu/content/begin/dna/transcribe/