If the procedure was performed correctly, how should the observed number of bands compare to the predictions?

If the procedure was performed correctly, how should the observed number of bands compare to the predictions?

• A. The bands should appear as a smear with no discrete bands.
• B. The bands should be more numerous than predicted.
• C. The bands should be identical in number to the predicted value.
• D. The bands should be fewer than predicted.

Answer: (C)

When analyzing DNA fragments on a gel, the number of distinct bands corresponds to the number of DNA fragments produced by the procedure. If everything is done correctly, the fragments produced should match the predicted set from the experiment design (for example, the known restriction sites or expected PCR product sizes). Each predicted fragment yields one band, so the observed count should align with the prediction. Seeing a smear would point to degraded DNA or poor gel conditions, not a mismatch with prediction. More bands than predicted usually means additional, nonspecific, or partially cut fragments. Fewer bands than predicted can happen if fragments co-migrate to the same size or if some fragments are missing due to incomplete digestion, but the expected outcome under correct technique is that the number of bands matches the predicted number.

When analyzing DNA fragments on a gel, the number of distinct bands corresponds to the number of DNA fragments produced by the procedure. If everything is done correctly, the fragments produced should match the predicted set from the experiment design (for example, the known restriction sites or expected PCR product sizes). Each predicted fragment yields one band, so the observed count should align with the prediction.

Seeing a smear would point to degraded DNA or poor gel conditions, not a mismatch with prediction. More bands than predicted usually means additional, nonspecific, or partially cut fragments. Fewer bands than predicted can happen if fragments co-migrate to the same size or if some fragments are missing due to incomplete digestion, but the expected outcome under correct technique is that the number of bands matches the predicted number.