Which techniques of the genetic engineering overcome the limitation and allows us to isolate and introduce only one one or a set of desirable genes without introducing undersirable genes into target organism ?

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for techniques in genetic engineering that allow the isolation and introduction of only desirable genes into a target organism, avoiding the introduction of undesirable genes.

2. **Recombinant DNA Technology**: One of the primary techniques is recombinant DNA technology. This involves isolating a specific gene of interest and combining it with a vector (like a plasmid) to create recombinant DNA. This method ensures that only the desired gene is introduced into the target organism.

3. **Gene Cloning**: Another important technique is gene cloning. In this process, the isolated gene is cloned to produce multiple copies. This allows for the introduction of a large amount of the desired gene into the target organism without the risk of incorporating unwanted genes.

4. **Direct Gene Transfer**: Direct gene transfer methods, such as microinjection, electroporation, or biolistics, can also be used. These methods allow for the precise introduction of the desired gene into the target organism's cells, minimizing the chance of introducing undesirable genes.

5. **Specificity of Techniques**: All these techniques are characterized by their specificity, which helps in avoiding the introduction of undesired genetic material into the target organism.

### Final Answer:
The techniques of genetic engineering that allow the isolation and introduction of only desirable genes into a target organism without introducing undesirable genes include:
1. Recombinant DNA technology
2. Gene cloning
3. Direct gene transfer methods

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