The gel presented here shows the pattern of bands of fragments produced with several restriction enzymes. The enzymes used are identified above the lanes of the gel, and six possible restriction maps are shown in the column to the right.
One of the six restriction maps shown is consistent with the pattern of bands shown in the gel.
From your analysis of the pattern of bands on the gel, select the correct restriction map and explain your reasoning.

Verified step by step guidance

1. Step 1: Understand the principle behind restriction mapping. Each restriction enzyme cuts DNA at specific sequences, producing fragments of characteristic sizes. When these fragments are run on a gel, they separate by size, creating a pattern of bands.
2. Step 2: Examine the gel lanes corresponding to each restriction enzyme. Note the number and sizes of the bands in each lane. These sizes represent the lengths of DNA fragments produced by cutting with that enzyme.
3. Step 3: Compare the observed fragment sizes from the gel with the predicted fragment sizes for each of the six possible restriction maps. For each map, calculate the expected fragment lengths by measuring the distances between restriction sites for each enzyme.
4. Step 4: Identify which restriction map's predicted fragment sizes match the band pattern on the gel for all enzymes. This map will have fragment sizes that correspond to the observed bands in every lane.
5. Step 5: Confirm your choice by ensuring that the combined fragment sizes for each enzyme add up to the total length of the DNA molecule, and that the pattern is consistent across all enzymes, supporting the selected restriction map.

Key Concepts

Restriction Enzymes and DNA Fragmentation

Restriction enzymes are proteins that cut DNA at specific sequences, producing fragments of varying lengths. Each enzyme recognizes a unique site, so digesting DNA with different enzymes results in distinct fragment patterns. Understanding how these enzymes cut DNA is essential for interpreting gel electrophoresis results.

Gel Electrophoresis and Band Patterns

Gel electrophoresis separates DNA fragments based on size, with smaller fragments migrating faster through the gel matrix. The resulting band pattern reflects the lengths of DNA fragments produced by restriction enzyme digestion. Analyzing these patterns helps infer the arrangement of restriction sites on the DNA.

Restriction Mapping

Restriction mapping involves determining the order and distance between restriction sites on a DNA molecule by analyzing fragment sizes from single and combined enzyme digests. By comparing observed band patterns to predicted fragment sizes, one can deduce the correct restriction map that matches the gel data.