What is the basis of selection in a plasmid-containing gene lac Z ?

Explanation

### Step-by-Step Solution:

1. **Understanding Plasmids**:
- Plasmids are small, circular, double-stranded DNA molecules that exist independently of chromosomal DNA within a cell. They are commonly found in bacteria and can replicate independently.

2. **Introduction to the lac Z Gene**:
- The lac Z gene is a gene found in the plasmid that encodes the enzyme beta-galactosidase. This enzyme is crucial for the metabolism of lactose and certain galactosides.

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