5. Genetics of Bacteria and Viruses

Describe the role of heteroduplex formation during transformation.

Penicillin was first used in the 1940s to treat gonorrhea infections produced by the bacterium Neisseria gonorrhoeae. In 1984, according to the CDC, fewer than 1% of gonorrhea infections were caused by penicillin-resistant N. gonorrhoeae. By 1990, more than 10% of cases were penicillin-resistant, and a few years later the level of resistance was at greater than 95%. Almost every year the CDC issues new treatment guidelines for gonorrhea that identify the recommended antibiotic drugs and dosages.

What are the long-term implications of these frequent changes in treatment recommendations for the patient population?

Penicillin was first used in the 1940s to treat gonorrhea infections produced by the bacterium Neisseria gonorrhoeae. In 1984, according to the CDC, fewer than 1% of gonorrhea infections were caused by penicillin-resistant N. gonorrhoeae. By 1990, more than 10% of cases were penicillin-resistant, and a few years later the level of resistance was at greater than 95%. Almost every year the CDC issues new treatment guidelines for gonorrhea that identify the recommended antibiotic drugs and dosages.

What are the short-term implications of these frequent changes for physicians and clinics that treat sexually transmitted diseases like gonorrhea and for individuals infected with gonorrhea?

Penicillin was first used in the 1940s to treat gonorrhea infections produced by the bacterium Neisseria gonorrhoeae. In 1984, according to the CDC, fewer than 1% of gonorrhea infections were caused by penicillin-resistant N. gonorrhoeae. By 1990, more than 10% of cases were penicillin-resistant, and a few years later the level of resistance was at greater than 95%. Almost every year the CDC issues new treatment guidelines for gonorrhea that identify the recommended antibiotic drugs and dosages.

Why is the CDC so active in making these recommendations?

In Bacillus subtilis, linkage analysis of two mutant genes affecting the synthesis of two amino acids, tryptophan (trp₂⁻) and tyrosine (trp₁⁻), was performed using transformation. Examine the following data and draw all possible conclusions regarding linkage. What is the purpose of Part B of the experiment? [Reference: E. Nester, M. Schafer, and J. Lederberg (1963).]

Define the term genetic complementation.

Give another example of genetic complementation and describe how genetic complementation works in that case.

In a cotransformation experiment, using various combinations of genes two at a time, the following data were produced. Determine which genes are 'linked' to which others.

For the experiment in Problem 26, another gene, g, was studied. It demonstrated positive cotransformation when tested with gene f. Predict the results of testing gene g with genes a, b, c, d, and e.

A wild-type culture of haploid yeast is exposed to ethyl methanesulfonate (EMS). Yeast cells are plated on a complete medium, and 6 colonies (colonies numbered 1 to 6) are transferred to a new complete medium plate for further study. Four replica plates are made from the complete medium plate to plates containing minimal medium or minimal medium plus one amino acid (replica plates numbered 1 to 4) with the following results:

Identify the colonies that are auxotrophic (mutant). What growth information leads to your answer? 

A wild-type culture of haploid yeast is exposed to ethyl methanesulfonate (EMS). Yeast cells are plated on a complete medium, and 6 colonies (colonies numbered 1 to 6) are transferred to a new complete medium plate for further study. Four replica plates are made from the complete medium plate to plates containing minimal medium or minimal medium plus one amino acid (replica plates numbered 1 to 4) with the following results:

Identify the colonies that are prototrophic (wild type). What growth information leads to your answer? 

How could antisense RNA be used as an antibiotic? What types of genes would you target using this scheme?