Question

Which of the following restriction endonucleases generates \(3'\) overhangs?

• A. EcoRI
• B. Hind III
• C. Pst I
• D. Sau 3AI

Hint:

Remember common restriction enzymes:
• EcoRI \(\rightarrow 5'\) overhang
• HindIII \(\rightarrow 5'\) overhang
• PstI \(\rightarrow 3'\) overhang
• SmaI \(\rightarrow\) Blunt ends \[ \text{Sticky ends improve efficiency of DNA ligation} \]

Answer 1

The Correct Option is C

Concept: Restriction endonucleases cut DNA at specific recognition sequences and may generate:
• Blunt ends
• \(5'\) overhangs
• \(3'\) overhangs A \(3'\) overhang is produced when the enzyme leaves a short single-stranded extension at the \(3'\) end of DNA.

Step 1: Understanding which enzyme produces \(3'\) sticky ends. Pst I recognizes the sequence: \[ 5' \; CTGCA|G \; 3' \] and cuts DNA in such a way that: \[ 3' \text{ overhangs are produced} \] Therefore: \[ \boxed{\textit{Pst I} \text{ generates } 3' \text{ overhangs}} \]

Step 2: Understanding the other restriction enzymes.
• EcoRI produces \(5'\) overhangs.
• Hind III also produces \(5'\) overhangs.
• Sau3AI generates \(5'\) sticky ends compatible with BamHI ends. Hence, among the given options, only Pst I produces \(3'\) overhangs. \[ \boxed{Pst I \Rightarrow 3' \text{ sticky ends}} \]