Understanding Restriction Enzyme Recognition

Restriction enzymes are essential tools in molecular biology, specifically in genetic engineering. These enzymes act like molecular scissors, cutting DNA at specific nucleotide sequences. The sequence that a restriction enzyme recognizes and binds to is called its recognition site. Many restriction enzyme recognition sites are palindromic, meaning they read the same forwards and backwards on opposite strands.

Analyzing the Palindromic DNA Sequence

The question asks us to identify the restriction enzyme that recognizes the palindromic sequence:

\(5'-GAATTC-3'\)
\(3'-CTTAAG-5'\)

Let's examine the options and their known recognition sites to find the match.

Restriction Enzyme Recognition Sites

Different restriction enzymes recognize distinct DNA sequences. Let's look at the recognition sites for the enzymes listed in the options:

• EcoRI: This enzyme is isolated from Escherichia coli. Its recognition site is \(5'-GAATTC-3'\). It cuts between G and A on both strands, producing sticky ends.
• HindIII: This enzyme is isolated from Haemophilus influenzae serotype Rd. Its recognition site is \(5'-AAGCTT-3'\). It also produces sticky ends.
• HindII: Also isolated from Haemophilus influenzae, HindII was one of the earliest restriction enzymes discovered. Its recognition site is \(5'-GTYRAC-3'\), where Y can be C or T (a pyrimidine), and R can be A or G (a purine). HindII typically cuts within the recognition site, producing blunt ends.
• BamHI: This enzyme is isolated from Bacillus amyloliquefaciens strain H. Its recognition site is \(5'-GGATCC-3'\). It produces sticky ends.

Matching the Sequence to the Enzyme

We are given the sequence \(5'-GAATTC-3'\). Comparing this sequence to the recognition sites listed above:

• EcoRI recognizes \(5'-GAATTC-3'\). This is a direct match.
• HindIII recognizes \(5'-AAGCTT-3'\). This is not a match.
• HindII recognizes \(5'-GTYRAC-3'\). This is not a specific match to GAATTC, as the variable bases Y and R make it a more degenerate sequence.
• BamHI recognizes \(5'-GGATCC-3'\). This is not a match.

Therefore, the enzyme that recognizes the specific palindromic sequence \(5'-GAATTC-3'\) is EcoRI.

Conclusion

Based on the analysis of the recognition sites, the restriction enzyme EcoRI is the enzyme that recognizes the palindromic sequence \(5'-GAATTC-3'\) / \(3'-CTTAAG-5'\).

Revision Table: Common Restriction Enzyme Recognition Sites

Additional Information: Types and Uses of Restriction Enzymes

Restriction enzymes are classified into different types (Type I, II, III, IV) based on their structure, recognition site, and mechanism of cutting. Type II enzymes, like EcoRI, HindIII, HindII, and BamHI, are the most commonly used in molecular biology because they cut DNA within their specific recognition sites. This precise cutting allows for the creation of predictable DNA fragments.

Key applications of restriction enzymes include:

• Gene cloning: Inserting DNA fragments into vectors (like plasmids) often requires cutting both the insert DNA and the vector DNA with the same restriction enzyme(s) to create compatible ends.
• Restriction mapping: Determining the relative positions of restriction enzyme sites on a DNA molecule.
• Restriction Fragment Length Polymorphism (RFLP) analysis: Used in genetic fingerprinting and disease diagnosis.
• Creating recombinant DNA for various biotechnological purposes.

Understanding the specific recognition sequences and cut sites of different restriction enzymes is fundamental for working with DNA in the lab.