Question

Polylinker DNA is one which
(A) Do not code for any protein
(B) Has restriction sites for several enzymes
(C) Is used for DNA transfer
(D) Is seen in single stranded DNA only

Answer 1

Hint: Polylinker DNA is also known as multiple cloning site(MCS), is a short segment of DNA which contains a lot of restriction sites (uniquely, occurring only once within a given plasmid). DNA sequence with several restriction enzyme recognition sites used in construction of different cloning or transformation plasmids.

Complete answer:
Option A Do not code for any protein
Noncoding DNA does not provide instructions for making proteins. Although non-coding DNA does not directly code for protein to be made, it serves to regulate genes which are responsible for making protein in many cases.

Option B-Has restrictions sites for several enzymes
A short DNA sequence which contains two or more different restriction sites for cleavage by restriction enzyme is called a polylinker. The enzymes involved are EcoRI, HindIII, BamHI etc. These recognise specific sites in DNA and make cuts at or near their recognisable sites.

Option C-Is used for DNA transfer
DNA transferring is done mainly during cell division. It is the mechanism by which DNA is passed from one generation of the cells to the next coming generation in simple words from parents to their offspring. In humans DNA is transferred as naked DNA, encapsulated DNA, or some time DNA with another organism.

Option D- Is seen in single stranded DNA
Single stranded DNA isolated from the phages is used for sequencing, site directed mutagenesis, or as a sequence-specific probe for detecting DNA. As polylinker DNA only has restrictions for the double stranded DNA.

Thus, the correct option is option B.

Note: Polylinker DNA are features that allow for the insertion of foreign DNA without disrupting the rest of the plasmid which makes it extremely useful in biotechnology. The plasmid vector is important as it permits cloning of restriction fragments generated by cleavage of DNA with different restriction enzymes.