Free Biotechnology Principles And Processes (Daily Quiz: 13) NEET Biology Questions & Answers with Detailed Explanation & Full Review

Answer: (a)

The presence of restriction sites within the markers tetr and ampr of plasmid permits an easy selection for cells transformed with recombinant plasmid. Insertion of the DNA fragment into the plasmid makes antibiotic resistance genes nonfunctional, for example, insertion of the DNA fragment into the plasmid (pBR322) using Pst I or Pvu I makes ampr nonfunctional. Bacterial cells containing such a recombinant pBR322 will be unable to grow in the presence of ampicillin, but will grow on tetracycline. This process, however, becomes burdensome because it requires simultaneous plating on two plates having different antibiotics. Thus, alternative selectable marker is developed to differentiate recombinants and non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substance. Here, a recombinant DNA is inserted in the coding sequence of an enzyme b-galactosidase. pUC 18 plasmid contains this gene which allows it to produce b-galactosidase which degrades certain sugars and produces a blue pigment when exposed to specific substrate analog. If the plasmid in the bacterium does not have an insert, i.e., is nonrecombinant, the presence of chromogenic substrate gives blue coloured colonies. Presence of insert in the plasmid in recombinant bacterium does not produce any colour, such bacterial colonies are marked as recombinant colonies.

Answer: (d)

Agrobacterium tumefaciens has been extensively used in genetic engineering experiments. It is the causative agent of crown gall, an important disease of many commercial crops. This disease has come to be recognized in recent years as being caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells. Following the discovery of the relationship between crown gall and the Ti plasmid, this plasmid has come to be widely used in plant genetic engineering as a vector in order to inject a novel gene in host plant to form a transgenic plant.

Answer: (c)

A : Hind III is a type II site-specific deoxyribonuclease restriction enzyme isolated from Haemophilus influenzae.

B : Transposons (also called jumping gene) is a chromosomal segment that can undergo transposition, especially a segment of bacterial DNA that can be translocated as a whole between chromosomal, phage, and plasmid DNA in the absence of a complementary sequence in the host DNA.

C : Bacteriophage is a virus which parasitizes a bacterium by infecting it and reproducing inside it.

D : Palindrome is a segment of double-stranded DNA in which the nucleotide sequence of one strand reads in reverse order to that of the complementary strand, eg, MALAYALAM.

Answer: (d)

EcoRI is an endonuclease enzyme isolated from strains of E.coli and a part of restriction modified system. So copart stands for coli.

Answer: (b)

EcoRV is a type II restriction endonuclease isolated from certain strains of E.coli. It creates blunt ends. It recognises the palindromic sequence of 6 bases as shown here:

SalI, XhoI and HindIII restriction enzymes produce sticky ends.