Which of the following is commonly used as a vector for introducing a DNA fragment in human lymphocytes ?

Options

A. `lambda` phage
B. Ti-plasmid
C. Retrovirus
D. pBR 322

Answer

C

Explanation

Usually a retrovirus is used as a vector for introducing a DNA fragment in human cells . They are used as vector in gene therapy to introduce the desired gene so as to replace the functioning of a desired gene so as to replace the functioning of a defected gene ,..e.g. Severe Combined Immune Deficiency (SCID) is caused due to defect in the gene for the enzyme adenosine deaminase .
In gene therapy against it , lymphocytes are extracted from the bone marrow of the patient .
These are grown in a culture outside the body . A functional ADA cDNA , using a retroviral vector , is then introduced into these lymphocytes . These are reinjected into the patient's bone marrow .
`lambda`-phage allows cloning of DNA fragments upto 23 Kb lengths. Ti-plasmid is usually used for plants . pBR- 322 is an artificial cloning vector , usually used for bacteria.