Q30 of 30 Page 1

(i) Describe the characteristics a cloning vector must possess.

(ii) Why DNA cannot pass through the cell membrane? Explain. How is a bacterial cell made ‘competent’ to take up recombinant DNA from the medium?


OR


If a desired gene is identified in an organism for some experiments, explain the process of the following:


(i) Cutting this desired gene at specific location.


(ii) synthesis of multiple copies of this desired gene.


i) The characteristics of a cloning vector are:-

a) Origin of replication (Ori) : It is a sequence which causes the initiation of replication and is also the place to link the foreign piece of DNA.


b) Selectable Marker : It is the site containing antibiotic resistance genes which helps us to identify the transformant and non-transformant vectors after the juncture of new piece of DNA.


c) Recognition Site: It is the cloning site where the piece of foreign DNA is inserted during the formation of Recombinant DNA molecule.


ii) DNA since being a hydrophilic molecule is unable to cross the bacterial cell membrane.


Various techniques used to transfer DNA into the cell are:-


a) By placing the cell in medium with high Ca2+ (divalent) ion concentration, which opens pore in cell membrane and allow entry of DNA into the cell.


b) By giving heat shock treatment i.e. putting the cell on ice and then immediately heated to 42 degree Celcius which opens pores and causes entry of DNA.


c) Micro-injection: Foreign DNA is directly injected into the cell using micro-needles.


d) Electroporation: Electric impulses induce pores on cell membrane through which DNA enters the cell.


e) Direct DNA Injection


f) Gene Gun/Biolistic: Small pellets of gold /tungsten are coated with DNA and hen bombarded on the cell at high velocity.


OR


i) Cutting the desired gene at specific location is done by Restriction enzymes i.e. restriction endonucleases.


They find the specific pallindromic sequence in the gene and cut it at the ends of the pallindromic sequence.


ii) Synthesis of this desired can be done transfering this gene into a bacterial cell for replication by the use of a plasmid.


The desired gene is first selected by electrophoresis and then introduced in the cell for production of multiple copies by the help of a vector i.e. a bacteriophage or a plasmid, etc.


More from this chapter

All 30 →
26

Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment.

OR


How do organisms cope with stressful external environmental conditions which are localised or of short duration?


 27

(i) State the consequence if the electrostatic precipitator of a thermal plant fails to function.

(ii) Mention any four methods by which the vehicular air pollution can be controlled.


 28

Give reasons why:

(i) Most zygotes in angiosperms divide only after certain amount of endosperm is formed.


(ii) Groundnut seeds are exalbuminous and castor seeds are albuminous.


(iii) Micropyle remains as a small pore in the seed coat of a seed.


(iv) Integuments of an ovule harden and the water content is highly reduced, as the seed matures.


(v) apple and cashew are not called true fruits.


OR


(a) Draw a labelled diagram of L.S. of an embryo of grass (any six labels).


(b) Give reason for each of the following:


(i) Anthers of angiosperm flowers are described as dithecous.


(ii) Hybrid seeds have to be produced year after year.


 29

Describe the mechanism of pattern of inheritance of ABO blood groups in humans.

OR


(a) Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.


(b) A pregnant human female was advised to undergo M.T.P. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX-egg fertilized by Y-carrying sperm. Why was she advised to undergo M.T.P.?