Lab 1: Bacterial Genetics Principles

Variations in bacteria that involve alteration of the DNA macromolecule are designated as temporary variations.

Phenotypic variations in bacteria disappear as soon as the environmental changes that brought them about disappear.

Mutations can be caused by UV light in sunlight or chemicals in the soil.

Permanent variations in bacteria are always caused by mutations.

Induced mutations are the result of the bacterium's exposure to a mutagen, which is a physical or chemical agent.

Urea, phenol, and various acids can be mutagens.

The antibiotic streptomycin is only present in the top layer of the gradient plate.

Staphylococcus aureus is resistant to streptomycin.

The gradient plate is prepared by pouring melted tryptic soy agar into a petri plate placed at an angle.

A 24-hour tryptic soy broth culture of Escherichia coli is required for this experiment.

Two tryptic soy broth tubes containing $50,\mu\mathrm{g}$ of streptomycin are needed for the experiment.

The procedure involves using a spreading rod to spread the bacterial culture on the gradient plate.

Ultraviolet light and x-rays are examples of physical agents that can act as mutagens.

A point mutation always results in a change in the amino acid sequence of the protein produced.

In an inversion mutation, a piece of DNA is replaced by an identical piece in reverse order.

A reversion mutation always results in the organism reverting back to its original phenotype.

A gradient plate is used to determine the ability of organisms to produce mutants that are resistant to antibiotics.

The tryptic soy agar should be labeled with the student's name and date.

The tryptic soy agar containing streptomycin should be poured onto the surface of the gradient-agar plate after it has solidified.

$0.5$ ml of the Staphylococcus aureus culture should be pipetted onto the agar surface.

The plate should be incubated at $37^\circ\mathrm{C}$ for $4$ to $7$ days in an open environment.

After incubation, resistant Staphylococcus aureus colonies should be observed in areas of higher streptomycin concentration.

Three control tubes should be inoculated with the initial Staphylococcus aureus culture: one without streptomycin, one with $10$ µg, and one with $50$ µg of streptomycin.