The meristem is the plant part that is best suited for making virus-free plants. This is because even when the plant is infected with a virus, the meristem (apical and axillary) remains infection free; it can be removed, grown in vitro to obtain virus-free plants. 

1. The tobacco plants show resistance to nematode attack; the nematode cannot survive in such plants, as they show RNA interference.
2. The vector used is Agrobacterium

(a) Positive terminal-B' Negative terminal-' A'
(b) DNA being negatively charged, moves towards the positive electrode (anode)
(c) By elution-separated bands of DNA are cut out from the agarose gel and extracted from the gel piece.

Origin of replication:
Origin of replication (Ori) is a specific sequence of DNA bases, which is responsible for initiating replication.
An alien DNA for replication should be linked to the origin of replication.
A prokaryotic DNA has normally a single origin of replication, while eukaryotic DNA may have more than one origin of replication

1. Taq polymerase is obtained from the bacterium Thermus aquaticus.
2. It is a thermostable enzyme, that can withstand the high temperature used in the denaturation and separation of the two strands of DNA; hence it can be used for a number of cycles of amplification.

The American company, Eli Lily used the following technique to produce synthetic human insulin or humulin. The steps followed were :
Two DNA sequences corresponding to A and B chains of human insulin were prepared and introduced into plasmids of E. coli. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin. 

(a) Transgenic animals are those animals, which have their DNA manipulated to possess and express one/ more foreign gene(s).
(b) Mica.
(c) They are produced for the following purposes:
(i) Transgenic animals are designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its development, e.g. information has been obtained as to how insulin has a role as growth factor.
(ii) Transgenic animals that produce useful biological compounds are created by introducing a portion of the DNA that codes for the product, e.g. a-I-antitrypsin is produced for treating emphysema.
(iii) Transgenic animals are being developed to test the safety of vaccines, e.g. polio vaccine has been tested on transgenic mice.
(iv) Transgenic animals with more sensitivity to toxic substances are being developed to test the toxicity of drugs.

(a) Origin of replication is the DNA sequence that serves as a start site for the replication process.
(b) The large customised tanks used to carry out the biological process/reaction at commercial scale are called as bioreactors.
(c) Downstream processing includes stages in the isolation and purification of the biotechnological products.

RNA interference is a gene-silencing process that blocks the expression of genes in the parasite when it enters the host's body.

(i)   A- Vector DNA/Plasmid DNA
b- Foreign DNA                     
(ii)  5'- GAATTAC-3'                
3'-CTTAAG-5'
(iii)  DNA ligase.   

Introduction of rDNA into host cell
(i) Microinjection
In this method, the recombinant DNA is directly injected into the nucleus of an animal cell.
(ii) Gene gun/Biolistics
In this method, used for plant cells, the cells are bombarded with high velocity microparticles of gold or tungsten coated with DNA.
(iii) Heat shock method In this method, the rDNA is forced into the competent cell by incubating the cell with rDNA on ice followed by placing them briefly at \({ 42 }^{ ° }C\) ( (heat shock) and then putting them back on ice.

(i) Palindromic sequence and the site where EcoRI cuts it (indicated by the arrows).
\({ 5 }^{ ' }{ G }^{ \downarrow }\begin{matrix} A & A \end{matrix}\begin{matrix} T & T \end{matrix}C\quad { 3 }^{ ' }\)
\({ 3 }^{ ' }C\begin{matrix} T & T \end{matrix}\begin{matrix} A & { A }_{ \uparrow } \end{matrix}G\quad { 5 }^{ ' }\)
(ii) Sticky ends

(i) Because Bt cotton is resistant to some insects and therefore it decreases the need of pesticides.
(ii) The advantages of genetically modified crops are:
(a) These are tolerant to abiotic stresses.
(b) These have enhanced nutritional value of food.
(c) These are resistant against some plant pathogens.
(d) These have reduced the use of chemical pesticides.

(i) Amplification of gene of interest using PCR is required.
(ii) Denaturation, annealing and extension are the basic steps of PCR.
(iii) Kary Mullis developed PCR in 1985
(iv) Honesty and sense of responsibility towards his duty.

(i) (b) : A patent is the right granted by a government to an inventor to prevent others from commercial use of his invention. Biopatent system allows private, monopoly rights over cells, genes, animals and plants.
(ii) (d) : Patents are supposed to satisfy three criteria of novelty, non-obviousness and utility.
(iii) (d) : Patents have been taken out on plants such as black pepper, basmati rice, Indian mustard, Pomegranate, Turmeric and neem.
(iv) (a)
(v) (a) : Genes, cells, micro-organisms, plants and animals are not inventions and hence must not be patented.

(a) It is a simple stirred-tank bioreactor.
(b) The curved base facilitates the mixing of the contents in the reactor.
(c) The stirrer facilitates even mixing and oxygen availability throughout the bioreactor.

(c) IfA is true, but R is false

(c): Yeast Artificial Chromosome (YACs) is a human engineered DNA molecule derived from the yeast. YACs are often used in connection with mapping and sequencing of genomes. Segments of an organism's DNA, upto one million base pairs in length, can be inserted into YACs. The YACs are then taken up by yeast cells. As the yeast cell grow and divide, they amplify the YAC DNA, which can be isolated and used for DNA mapping and sequencing.