Question 2 of 10intermediate✨ CreateDiagram5 marks

Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.

Correct Answer

Chart: Action of Restriction Endonuclease Enzyme (EcoRI)

1. Restriction Enzyme: The enzyme shown is EcoRI - a restriction endonuclease isolated from Escherichia coli bacteria. Restriction enzymes belong to a larger class of enzymes called nucleases (specifically endonucleases) that make cuts at specific positions within the DNA.

2. Substrate DNA: The substrate is a double-stranded DNA molecule containing the specific recognition sequence. EcoRI inspects the length of the DNA sequence to find its specific target.

3. Recognition and Cutting Site: EcoRI recognises a specific palindromic nucleotide sequence: 5'-GAATTC-3' on one strand and 3'-CTTAAG-5' on the complementary strand. The enzyme cuts the DNA between bases G and A only when this sequence is present. It cuts both DNA strands at the same site in the sugar-phosphate backbone.

4. Product Formed: The products are DNA fragments with sticky ends - single-stranded overhangs that are complementary to each other. These sticky ends can be joined with other DNA fragments cut by the same restriction enzyme using DNA ligase to form recombinant DNA.

Diagrammatic Representation:

Before Cutting:
5'---G A A T T C---3'
3'---C T T A A G---5'
        ↓ EcoRI
After Cutting:
5'---G        A A T T C---3'
3'---C T T A A        G---5'
       ← Sticky Ends →
Exercise: EXERCISES | Q: 2 | (Page 15)
For More Understanding

Explanation

This answer addresses all four components requested in the question: (1) the restriction enzyme EcoRI, (2) the substrate DNA it acts upon, (3) the specific palindromic recognition sequence and cutting site between G and A, and (4) the product - DNA fragments with sticky ends. The context from the textbook explains that restriction endonucleases recognise specific palindromic sequences and cut both strands at specific points in their sugar-phosphate backbones. The sticky ends produced allow DNA fragments from different sources to be joined together using DNA ligase to form recombinant DNA molecules.

Solution Steps

  1. Step 1: Identify the restriction enzyme (EcoRI) and its origin

  2. Step 2: Describe the substrate DNA with its double-helical structure

  3. Step 3: Explain the palindromic recognition sequence (GAATTC) and cutting site (between G and A)

  4. Step 4: Describe the product - DNA fragments with sticky ends

  5. Step 5: Provide a simplified diagrammatic representation showing the cutting process

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