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.

What does cloning mean?

1.      The ability to multiply the desired gene in the host

2.      The ability to multiply the vector in the host

3.      The ability to multiply the antibiotic resistance gene in the host

4.     The ability to multiple Ori in the host

The normal E. coli cells have

1.      Kanamycin

2.      Tetracycline

3.      Ampicillin

4.     No resistance

In order to make the host cell competent

Divalent cations such as calcium are used-

1.      The divalent ions have to be in a specific concentration

2.      They cause the DNA uptake by the cell

3.      They increase the efficiency with which DNA enters the bacterium through pores in its cell wall.

4.     All of the above

The process of competent cell formation include

1.      CaCl2 treatment- ice incubation with r-DNA, heat shock at 42 degree Celsius, ice incubation

2.      Ice incubation - CaCl2 treatment - Heat shock-Ice incubation with r-DNA

3.      CaCl2 treatment - Heat shock -Ice incubation with r-DNA

4.     Ice incubation - CaCl2 treatment - Heat treatment at 45 degree Celsius, Ice incubation with r-DNA

DNA precipitation, out of a mixture of biomolecules, can be achieved by treatment with:
1. Chilled chloroform
2. Isopropanol 
3. Chilled ethanol
4. Methanol at room temperature