Q7 EcoRI enzyme recognizes the sequence GAATTC. A stretch of linear DNA with six GAATTC sites, upon
digestion with EcoRI, will give rise to
1. 8 fragments
2. 7 fragments
3. 6 fragments
4. 5 fragments

EcoRI Enzyme Digestion and Fragment Formation in Linear DNA

EcoRI is one of the most widely used restriction enzymes in molecular biology. It plays a crucial role in DNA fragmentation and gene cloning experiments. Understanding how EcoRI digestion works is essential for competitive exams like CSIR NET Life Science, IIT JAM, GATE Biotechnology, and DBT JRF. In this article, we will explore how EcoRI functions and how to calculate the number of fragments produced during digestion.

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What is EcoRI Enzyme?

EcoRI is a restriction endonuclease isolated from the bacterium Escherichia coli. It recognizes the specific palindromic DNA sequence:

5’ – GAATTC – 3’

and cuts between the G and the A on each strand, creating sticky ends:

5’ – G AATTC – 3’
3’ – CTTAA G – 5’

EcoRI is highly specific and generates fragments with cohesive ends, making it ideal for cloning and recombinant DNA technology.

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How EcoRI Digestion Works on Linear DNA

1. Linear DNA Structure

Linear DNA molecules have two free ends. When EcoRI recognizes its target sequence (GAATTC), it cleaves at the specific site, creating fragments.

2. Number of Fragments Calculation

• If a linear DNA molecule has N recognition sites, EcoRI will generate N + 1 fragments after digestion.
• Example:
  • A linear DNA with 6 EcoRI sites will produce 6 + 1 = 7 fragments upon complete digestion.

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Correct Answer:

✅ Option 2: 7 fragments
A linear DNA molecule with 6 EcoRI recognition sites will generate 7 fragments after complete digestion.

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EcoRI Enzyme in Molecular Biology

EcoRI is widely used in molecular biology for:

1. DNA Cloning

• EcoRI creates sticky ends, allowing easy ligation of DNA fragments into vectors.
• Sticky ends increase the efficiency of recombinant DNA formation.

2. Restriction Mapping

• EcoRI digestion helps in creating restriction maps of DNA molecules.
• Digested fragments can be separated using gel electrophoresis to estimate fragment size and sequence arrangement.

3. Genetic Engineering

• EcoRI is used in site-specific gene modification.
• It helps in inserting foreign genes into host DNA for gene expression studies.

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Example Problem on EcoRI Digestion

Question: A linear DNA molecule contains 4 EcoRI sites. How many fragments will be produced after digestion with EcoRI?
Solution:

• Number of recognition sites = 4
• Fragments produced = 4 + 1 = 5 fragments

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Importance of EcoRI Digestion in CSIR NET and Other Exams

EcoRI digestion and fragment calculation are frequently tested in competitive exams like:

• CSIR NET Life Science
• IIT JAM Biotechnology
• GATE Biotechnology
• DBT JRF

Mastering the concept of restriction enzyme digestion is essential for securing high marks in these exams.

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Conclusion

EcoRI enzyme digestion is a critical tool in molecular biology. A linear DNA molecule with N recognition sites will produce N + 1 fragments after digestion. Understanding EcoRI’s specificity and fragment formation mechanism is essential for success in molecular biology-related questions in CSIR NET, IIT JAM, GATE, and DBT JRF exams. For expert guidance and structured study material, enroll at Let’s Talk Academy – the leading institute for life science preparation.