Question

1. When transforming cells, what are three possible outcomes in terms of the genetic makeup of the cells? How can we select for cells that take up a vector?

Answer 1

THREE POSSIBLE OUTCOMES ARE :-

1. non-transformant

cloning vector not present in host cell .

2. transformant ( non - recombinant)

cloning vector present in host cell but ligation had not occured i.e., cloning vector has not ligated with foreign DNA.

3. transformant (recombinant)

cloning vector present in host cell and ligation had occured i.e., cloning vector has ligated with foreign DNA.

Process of selection

Generally, antibiotic resistance encoding gene of cloning vector is used for selection between transformant and non- transformant and recombinant and non- recombinant.

Eg.- ampR , tetR encoding gene in case of pBR322.

1.Bacterial cell grown in ampicillin contaning medium.

Purpose: To separate transform cell from non- transformed cell.

Result: Non- transformant cell: Killed.

Transformant: Survive.

2. Host cell transferred in tetracycline medium.

Purpose: To select recombinant cell from non— recombinant cell.

Result: Non- recombinant cell: Survive.

Recombinant cell: Killed.

Reason: Because, tetracycline resistance encoding gene has been insertional inactivated.