Question

Identify the plasmid from the following
A.AIU I
B.Hind III
C.Eco RI
D.pBr 322

Answer 1

Hint: Plasmid is a double stranded DNA molecule that is separated from chromosomal DNA. They are capable of independent replication.

Complete answer:
Plasmid is a small circular particle which consists of double stranded DNA and it is physically distant from the cell’s chromosomal DNA. They are usually found in bacteria,but sometimes they are also found in some eukaryotic and archaea organisms. Every bacterial cell has a plasmid and they replicate independently and they are transferred during the conjugation process. The number of copies and size differs from cell to cell. Plasmids add to the peculiar characteristics of cells but they are not necessary for survival. But plasmids are widely used in genetic engineering techniques such as for producing many copies of DNA segments,as a cloning vector,for gene transfer etc. They are used for DNA cloning and replication etc because plasmids contain multiple cloning sites and replication sites into which a foreign DNA fragment ,that needs to replicate or cloned , will be inserted. They also contain certain antibiotic resistance genes in them which can be integrated with DNA fragments or other organisms to make it antibiotic–resistant. Now let's analyse the options to find out the correct option.
Option A) AIU I is not a plasmid. Therefore this is an incorrect option
Option B) Hind III is a restriction enzyme which is site specific. They produce cuts at the restriction site. Their function is to protect the host from invasion of foreign DNA, mainly the bacteriophage DNA. Therefore this is an incorrect option
Option C) Eco RI is also a restriction enzyme that produces cuts at the restriction site. It produces cuts in the DNA double helices and turns them into fragments. Therefore this is an incorrect option
Option D) pBr 322 is a plasmid vector that is used to carry genes to the bacterium and binds with it to provide peculiar characteristics such as resistance to antibiotics. Therefore this is the correct option

Hence, the correct answer is option (D)

Note: pBr 322 consist of restriction enzymes HindIII and EcoRI and also 2 antibiotics resistance gene ampicillin and tetracycline.An ori site is present for replication. There are also sites for cloning which is mainly used for cloning in E Coli bacteria.. The size of this vector is 4361bp.