Question

1. Why do plasmid vectors contain a polylinker?

		So that the plasmid can be cut into many small fragments to be inserted in the region of interest
		To allow the plasmid to survive on antibiotic media
		To find a restriction enzyme site that is useful for inserting the fragment of interest
		Multiple cut sites are required for the DNA fragment to be inserted.

2.What does blue color mean in blue-white screening with pUC18?

		The DNA fragment was successfully inserted into the plasmid vector
		The DNA fragment was not successfully inserted into the plasmid vector
		The bacteria was not successfully transformed with the plasmid vector
		The bacteria was successfully transformed with the plasmid vector

3. cDNA is synthesized from what single stranded molecule?

Answer 1

ans

1. a is true.

A polylinker is a short DNA sequence which contains two or more different sites for cleavage by restriction enzymes. These are introduced into vectors, so that cleavage of DNA with multiple different restriction enzymes is possible. The plasmid vectors contain a polylinker, So that the plasmid can be cut into many small fragments to be inserted in the region of interest.

b. A polylinker doesnot help plasmid to survive in antibiotic media.

c. polylinker itself helps in cleavage with many restriction enzymes. so it doesn't help in finding one restriction enzyme.

d. DNA fragment can be inserted by cutting at specific sites.

2. b is true.

The blue-white screen is a technique that allow the detection of successful ligations in vector-based gene cloning. DNA of interest is ligated into a vector. If the ligation was successful, the bacterial colony will be white; if not, the colony will be blue. This technique used for the detection of successful ligation.

so, option b is true which says the DNA was not successfully inserted into plasmid.

3. messenger RNA ( mRNA) is a single stranded molecule which is used in synthesizing complementary DNA (cDNA).