Enzyme Experts
What is a restriction enzyme?
An enzyme that recognizes and cuts DNA at specific sequences.
What is the purpose of agarose gel electrophoresis?
To separate DNA fragments based on size.
Which sample contains the greatest number of DNA fragments?
Sample B (3 fragments).
DNA moves toward the wells instead of away from them. What is wrong?
The electrode connections are reversed.
What PPE should you wear during a biotechnology lab?
Appropriate PPE such as lab coat, gloves, and safety glasses according to lab procedures.
What is a recognition sequence?
A specific DNA sequence that a restriction enzyme recognizes and cuts.
DNA moves toward which electrode during electrophoresis?
The positive electrode.
Which DNA fragment size travels the farthest through the gel?
200 bp.
A DNA sample floats out of the well when loaded. What might be wrong?
Loading buffer may be missing or incorrectly prepared.
What equipment measures and transfers very small liquid volumes?
A micropipette.
What is the difference between sticky ends and blunt ends?
Sticky ends have exposed overhanging bases; blunt ends have straight cuts with no overhangs.
Why does DNA move toward the positive electrode?
DNA has a negatively charged phosphate backbone.
Which samples contain a 1,000 bp fragment?
Samples A and D.
A student sees very faint DNA bands. Give one possible reason.
Too little DNA was loaded, or there was insufficient staining/detection.
Why should the wells be positioned near the negative electrode?
DNA is negatively charged and needs to migrate toward the positive electrode.
EcoRV recognizes GATATC. How many base pairs are in this recognition sequence?
6 base pairs
Which travels farther: a 200 bp fragment or a 1,000 bp fragment? Why?
The 200 bp fragment because smaller fragments move more easily through the gel.
Which has the greatest total DNA fragment length: Sample A or Sample C? Show your work.
Sample A: 1,000 + 600 = 1,600 bp. Sample C: 600 + 400 = 1,000 bp. Sample A
A student sees a smear instead of distinct DNA bands. Give one possible cause.
DNA degradation, overloading, or inappropriate electrophoresis conditions.
Why should you avoid puncturing the agarose gel when loading DNA?
It can damage the well and cause the sample to leak into the buffer.
A scientist digests a linear DNA molecule with a restriction enzyme. The enzyme cuts at three recognition sites. How many DNA fragments will be produced?
4 fragments. The number of fragments is one greater than the number of cuts for linear DNA.
What is a DNA ladder, and why is it important?
A collection of DNA fragments of known sizes used to estimate the sizes of unknown DNA fragments.
What can scientists learn by comparing DNA banding patterns?
Whether DNA samples have similar or different fragment patterns, which can help compare biological samples.
A student forgets to load the DNA ladder. Why is this a problem?
There is no reference of known fragment sizes to estimate the sizes of the unknown DNA fragments.
Your lab partner wants to leave without cleaning the workspace or disposing of materials properly. Identify two workplace responsibilities they are neglecting.
Accountability, organization, cleanliness, safety, and proper waste disposal.