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student wanted to investigate the effect of two different endonucleases (restriction enzymes) on a linear DNA fragment - VCE - SSCE Biology - Question 11 - 2020 - Paper 1
Question 11
student wanted to investigate the effect of two different endonucleases (restriction enzymes) on a linear DNA fragment. The student used three tubes containing a buf... show full transcript
Worked Solution & Example Answer:student wanted to investigate the effect of two different endonucleases (restriction enzymes) on a linear DNA fragment - VCE - SSCE Biology - Question 11 - 2020 - Paper 1
Step 1
What conclusions can be drawn from the DNA fragments produced by BamHII and HindIII?
Answer
In this experiment, the two endonucleases BamHII and HindIII produced different fragment patterns.
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Comparison of Fragment Sizes: BamHII cuts the DNA fragment in one place, producing two fragments: 4000 bp and 5500 bp. HindIII cuts the DNA fragment in two places, resulting in multiple fragments: 8000 bp, 1000 bp, and additional smaller fragments down to 250 bp.
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Movement of Fragments: The shorter fragments move further during the electrophoresis due to their lighter mass. Hence, in the gel, we can observe that the smaller pieces have migrated closer to the bottom of the gel.
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Collective Results: When both endonucleases are present, as in Tube 3, the anticipated results yield four fragments based on the cumulative cuts from the two enzymes, showing a variety of sizes proportional to their respective contributions.
Step 2
What could be the reason for the absence of bands in Tube 1?
Answer
The absence of bands for BamHII in Tube 1 may indicate that:
- The sample might not have been loaded properly into the well, resulting in no enzyme activity visible in the gel.
- Potential degradation of the DNA sample before the run, which could lead to no observable product on the gel.
Step 3
What could be the reason for only one band for HindIII in Tube 2?
Answer
Only one band for HindIII in Tube 2 may suggest that the restriction enzyme became denatured during the reaction, inhibiting its ability to cut the DNA fragments effectively.
Alternatively, it could indicate that the DNA was not cut adequately due to optimal conditions not being met, like temperature or incubation time.
Step 4
What factors determine the size or length of the fragments produced?
Answer
The size or length of the fragments produced can depend on several factors:
- Size of the DNA Fragments: The position where the enzymes cleave the DNA affects the resulting fragment sizes.
- Agarose Gel Properties: The concentration and viscosity of the agarose gel will impact the movement and separation of the DNA fragments during electrophoresis.
- Voltage or Power Used: The voltage applied during the gel run influences how far the fragments travel; higher voltage can lead to faster separation but may also cause overheating.
Step 5
What safety precautions should be taken during this experiment?
Answer
The following safety precautions should be observed:
- Electrophoresis Setup: Ensure that the electrophoresis equipment is set up correctly to avoid electrocution risks.
- Protective Gear: Wearing safety goggles and gloves is imperative to protect against exposure to chemicals or contamination.
- Proper Disposal: Follow proper disposal protocols for any contaminated material, including used gels and samples, to avoid environmental hazards.
- Knowledge Application: It's important to understand the safe handling of biological specimens and the chemicals involved.