Each restriction endonuclease functions by inspecting the length of a DNA sequence . It cleaves __________

Options

A. Only the master strand to produc sticky end
B. Sense strand of DNA to produce sticky ends
C. Each of the two strands of the double helix at specific points in their sugar phosphate backbones
D. Messenger RNA to remove exons

Answer

To answer the question, "Each restriction endonuclease functions by inspecting the length of a DNA sequence. It cleaves __________," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are proteins that cut DNA at specific sequences. They are often referred to as "molecular scissors."

2. **Identifying the Function**:
- These enzymes recognize specific sequences within the DNA, known as recognition sites or restriction sites. Each restriction enzyme has a unique recognition site where it will cleave the DNA.

3. **Cleavage Mechanism**:
- The cleavage occurs at the sugar-phosphate backbone of the DNA. This means that the enzyme breaks the phosphodiester bonds between the nucleotides.

4. **Double-Stranded DNA**:
- Importantly, restriction endonucleases cut both strands of the double helix at the same location, which is essential for producing fragments that can be used in various biotechnological applications.

5. **Sticky Ends vs. Blunt Ends**:
- Depending on the restriction enzyme, the cut can produce "sticky ends" (overhanging ends) or "blunt ends" (straight cuts). However, the question specifically asks about the cleavage process itself.

6. **Final Answer**:
- Therefore, the correct completion of the statement is: "Each restriction endonuclease functions by inspecting the length of a DNA sequence. It cleaves **each of the two strands of the double helix at a specific point on the sugar and phosphate backbone**."