Plasmid Analysis Worksheet

Biology 102 Lab #4

1. Attach a photo of your gel to this worksheet. Be sure each lane is labeled with the appropriate strain name, and also label the 1-kb ladder fragments you were able to distinguish with their sizes.

2. Attach your standard curve to this worksheet. Check the Biology Student Handbook carefully to be sure you have done the curve correctly. Distance migrated should be measured in mm (to the nearest 0.1 mm), and fragment size should be on a logarithmic scale. You should include a best-fit line and its equation.

3. Using your standard curve, fill in the table below with the sizes of the DNA fragment(s) produced by EcoRI digestion of the plasmid DNA from each strain. Then give the total length of each plasmid.

Strain / DNA fragment length(s) (bp) / Plasmid length (bp)
MC1000
UC19
ACYC184
JV114

4. Fill in the table below with your antibiotic resistance data (diameters of zones of inhibition in mm). Compare each strain to MC1000, our reference strain, and decide whether it is more resistant to each antibiotic, less resistant or the same as MC1000.

Antibiotic
Streptomycin / Tetracycline / Ampicillin / Chloramphenicol
Strain / Diameter / Resistance* / Diameter / Resistance / Diameter / Resistance / Diameter / Resistance
MC1000 / — / — / — / —
UC19
ACYC184
JV114

* Resistance: R = more resistant than MC1000; S = more susceptible than MC1000; — = same resistance as MC1000


5. Antibiotic resistance could be due to a resistance gene located on a plasmid or a resistance gene located on the chromosome of the bacterial cell. For each strain and antibiotic you labeled “R” above, tell whether you think the resistance is likely to be due to a plasmid gene or a chromosomal gene, and give the evidence that supports your conclusion.

6. How could you demonstrate experimentally that the resistance of a particular strain to a particular antibiotic is due to the plasmid you isolated? Briefly describe an experiment that would allow you to determine whether the plasmid you isolated actually contains an antibiotic-resistance gene.