Restriction enzyme ECoRI cleaves DNA at the sequence

Options

A. AAGCTT
B. AAGTTC
C. GTATATC
D. GAATTC

Answer

**Step-by-Step Solution:**

1. **Identify the Restriction Enzyme**: The restriction enzyme in question is ECoRI, which is derived from the bacterium *Escherichia coli*.

2. **Recognize the Cleavage Sequence**: ECoRI specifically recognizes and cleaves the DNA at the palindromic sequence: GAA TTC.

3. **Understand the Cleavage Mechanism**: ECoRI cuts between the G and A nucleotides in the recognition sequence, resulting in two single-stranded DNA ends with the sequence AATT.

4. **Clarify the Nature of the Enzyme**: ECoRI is classified as a restriction endonuclease, which means it can cut DNA at specific sequences, creating fragments.

5. **Explain the Origin of the Name**: The name ECoRI is derived from the organism it was isolated from (*E. coli*) and the specific strain (R).

6. **Summarize the Function**: ECoRI is part of the restriction-modification system in bacteria, which serves as a defense mechanism against foreign DNA.

**Final Answer**: The restriction enzyme ECoRI cleaves DNA at the sequence GAA TTC.

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