Lecture 10: Bacterial genetics
1. Describe four distinctly different ways in which genes can be transferred into a bacterial cell.
2. What is the shape of the linkage map of E. coli? How has this been shown?
3. What is the difference between an F+ strain and an Hfr strain? Which is the most useful in bacterial genetic analysis and why?
4. What units are normally used to measure map distances in E. coli ? What is the basis for use of this particular type of unit?
5. What is a merozygote and what is its value in genetic research?
6. What type of bacterial mating system is used to generate stable partially diploid cells?
7. How does genetic transduction differ from transformation?
8. What was the nature of the first experimental evidence showing that DNA was capable of carrying genetic information?
9. What is an auxotrophic mutation? What term is used to describe
the corresponding non-mutant state?
10. Explain how the inability to utilize a particular substrate can be used as a genetic marker in bacteria.
11. The E. coli genome has been completely sequenced.
a. How large is the genome of E. coli?
b. How many times as large is the human genome compared to that of E. coli. (The human genome contains about 3.0 x 109 base pairs).
c. How many potential protein-coding genes are contained in the E. coli genome (see table 7.3).
d. If the human genome contained a comparable density of genes per amount of DNA, how many genes would be in the human genome?
e. A recent news report suggested that the number of human genes could be as large as 140,000 (significantly higher than previous estimates of less than 100,000). What can you conclude about the density of genes in human DNA relative to that in E. coli DNA?
12. Describe a selective medium scheme for isolation of each of the following types of mutations.
a. a leucine auxotroph
b. a strain unable to utilize lactose
c. a strain that is resistant to ampicillin (an antibiotic)
d. a strain that is resistant to infection by a specific type of bacteriophage.
e. A cell from a strain auxotrophic for leucine that had been transformed to prototrophy with purified DNA from a proptotrophic strain.
13. In many cases, Hfr conjugation can transfer several bacterial genes to a recipient cell without the recipient cell becoming an Hfr cell. Explain how this can happen.
!4. Explain how merozygotes can be used for complementation studies. Be sure that your answer makes it clear that you understant what complementation is.
15. Distinguish between lytic and lysogenic bacteriophage infections in a manner that makes it clear that you understand what each is and how they differ.
16. Distinguish between specialized transduction and generalized transduction in a manner that makes it clear you know what each is and how they differ.
17. What is the smallest known genome size for a free-living organism? How many protien coding units does it contain?
18. Distinguish between virulent and temperate bacteriophages in a manner that makes it clear that you know what each is and how they differ.
19. Explain the process that gives rise to turbid plaques by temperate bacteriophages.
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