Question

Which of the following is used to deliver genes in animal cells?

• A. Ti plasmid
• B. Disarmed retroviruses
• C. Bacteriophage vectors
• D. Both b and c

Answer 1

The correct option is B Disarmed retroviruses

Retroviruses are viruses with RNA as their genetic material. Once it has infected a cell, it converts its RNA into cDNA (complementary DNA) by reverse transcription. This DNA then integrates into the DNA of the host cell which later encodes for desired proteins.
Retroviral vectors are genetically engineered retroviruses which are made to carry foreign genes. Their own genes which may cause harm to animal cells are removed or disarmed. They have been used for the transfer of genes into the animal cells.

Tumor inducing (Ti) plasmid is present in Agrobacterium tumefaciens which is a pathogen of several dicot plants. This bacteria naturally delivers its “T-DNA” piece of Ti plasmid to the host. This leads to the transformation of normal plant cells into tumor cells to produce chemicals required by the bacterial pathogen. This Ti plasmid of Agrobacterium tumefaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to deliver our genes of interest into a variety of dicot plants.

Bacteriophages are being used as vectors for bacteria. They can also carry foreign DNA fragments and have high copy numbers.