A host cell normally does not take up a foreign DNA until it has been made competent to do so. This is because:

1. DNA is a hydrophilic molecule

2. DNA is a very large molecule

3. there are no receptors for DNA on the cell membrane

4. DNA is an inert molecule

Microbes found to be very useful in genetic engineering are:

1. Escherichia coli and Agrobacterium tumefaciens

2. Vibrio cholerae and a tailed bacteriophage

3. Diplococcus sp. and Pseudomonas sp.

4. Crown gall bacterium and Caenorhabditis elegans

 E.coli is  a commonly used host for gene cloning because

1. It is free from elements that interfere with replication and recombination of DNA

2. It is easy to transform

3. It supports replication of inserted DNA.

4. All of these

Two bacteria found to be very useful in genetic engineering are

If you transform a cell with an alien piece of DNA only, What is the possibility?

1.      This alien piece becomes a part of the host genome.

2.      It doesn't become a part of the host's genome but keeps on replicating

3.      The cloning of genes won't get affected in the absence of Origin of replication.

4.     Multiple identical copies of an alien piece of DNA can be formed irrespective of its integration into the host's genome.