The cutting of DNA at specific locations became possible with the discovery of

Options

A. Ligases
B. Restriction enzymes
C. Probes
D. Selectable markers

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the discovery that made it possible to cut DNA at specific locations. This is a fundamental aspect of biotechnology and genetic engineering.

2. **Identifying Key Terms**: The options provided are ligases, restriction enzymes, probes, and selectable markers. Each of these plays a different role in molecular biology.

3. **Analyzing Each Option**:
- **Ligases**: These are enzymes that join DNA fragments together but do not cut DNA.
- **Restriction Enzymes**: These are enzymes that can cut DNA at specific sequences, known as recognition sites.
- **Probes**: These are short sequences of DNA or RNA that can bind to specific sequences but do not cut DNA.
- **Selectable Markers**: These are genes used to identify transformed cells but do not involve cutting DNA.

4. **Conclusion**: Based on the analysis, the correct answer is **restriction enzymes**. They are crucial in recombinant DNA technology for cutting DNA at specific sites, allowing for the manipulation of genetic material.

5. **Example of Restriction Enzyme**: One of the first discovered restriction enzymes is HindII, which recognizes and cuts the DNA sequence CTCGAG.

6. **Importance in Biotechnology**: The ability to cut DNA at specific locations has enabled significant advancements in genetic engineering, allowing scientists to create recombinant DNA, clone genes, and conduct various genetic modifications.