What are selectable markers? Give two examples.

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Selectable Markers:**
Selectable markers are specific genes used in genetic engineering that allow for the identification and selection of cells that have successfully incorporated a foreign DNA fragment. They help differentiate between transformed (successfully modified) and non-transformed (non-modified) cells.

2. **Function of Selectable Markers:**
When a DNA fragment is inserted into a vector (like a plasmid), the selectable marker gene is used to determine whether the transformation has occurred. If the transformation is successful, the host organism will express the selectable marker, allowing it to survive in conditions that would normally kill non-transformed cells.

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