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Ori (origin of replication) is the specific DNA sequence where the replication of DNA is initiated. Therefore for multiplication of alien DNA in the host it has to be integrated to the ori (origin of replication).

It is because of Cry proteins produced by the spores of Bacillus thuringiensis which are toxic when ingested by some insects.

Sickle cell anaemia.

1. pBR 322

2. amp – ampicillin resistant gene^R, tet^R tetracyclin resistant gene.

Answer is (b) Hind II

Gel Electrophoresis

Genes are transferred from bacterium or virus to eukaryotic cells and these genes force the transformed cell to works at their will

eg: Agrobacterium mediated gene transfer.

Yes, they move towards anode (positively charged) because the DNA fragments are negatively charged.

Ethidium bromide (EtBr) exchanges its visible range of wavelength with the invisible wave length of DNA to make it visible under UV light.

The restriction enzymes are known as molecular scissors as they cut the DNA at specific sites or locations. 

They help (in genetic engineering) to form recombinant molecules of DNA, which are composed of DNA from different genomes.

Basis of technique :Since DNA fragment are negatively charged, they can be separated by forcing them to move towards the anode under an electric field through a medium of matrix (agarose).

Uses:

(a) The purified DNA fragments obtained by gel electrophoresis.

(b) They are used in DNA fingerprinting.

In gel electrophoresis, DNA fragments are negatively charged molecules. They can be separated by forcing them to move towards the anode under electric field through a medium/ matrix.

1. Restriction endonucleases

2. DNA Iigases

DNA molecules are bigger in molecular size as compared to molecular size of enzymes. It is because an enzyme (protein) is synthesized from the segment of DNA called gene.

DNA ligase is a vital enzyme required for important cellular process such as DNA replication, repair of damaged DNA and recombination. The enzyme mediates the formation of phosphodiester bonds between adjacent 3'-OH and 5'-phosphate termini, thereby joining the nicks in double-stranded DNA.

(a) Plasmid DNA : The construction of the first recombinant DNA molecule emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid of Salmonella typhimurium. Stanely Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid that was responsible for conferring antibiotic resistance. 

(b) Recognition sequences : The first restriction endonuclease HindII, whose functioning depended on a specific DNA nucleotide sequence, was isolated and characterized five years later. This specific base sequence is known as the recognition sequence for HindII. 

(c) Gel electrophoresis : The cutting of DNA by restriction endonuclease results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. 

Cohen and Boyer isolated the antibiotic resistant gene, from the plasmid of a bacterium that was resistant to the antibiotic drug and then linked this gene with the plasmid of Salmonella typhimurium, construction of artificial recombinant DNA molecule.

(a) (i) To take up the (hydrophilic) DNA from the external medium. 

(ii) Divalent calcium ions increase the efficiency the cell through pores in the cell wall.

(b) To introduce alien DNA into the plant cell by bombarding them with high velocity microparticles (gold or tungsten coated with DNA).

Detailed Answer :

(a) In biotechnology experiments, the cells must be made competent so that they can take up the hydrophilic DNA molecule inside them from the external medium. Treatment of bacterial cells with divalent calcium cations makes them competent and helps them to take up the DNA through the pores in the cell wall. 

(b) Biolistic gene or gene gun is a method of introducing alien DNA into the plants cells. In this method, the host cells are bombarded with high velocity micro-particles of gold and tungsten coated with DNA molecules.

Plasmids are commonly used to multiply or express particular genes and act as vectors to transfer piece of foreign DNA attached to them.

Cut fragments of DNA can be segregated/separated. 

1. Simple stirred tank bioreactor

2. Sparged stirred tank bioreactor

The stirrer facilitates mixing of content and o₂ availability.

In human being the concentration of DNA is 0.4%. It contains 6.6 × 10⁹ bp.

(a) Multiple copies of gene of interest can be obtained.

(b) They can cut DNA molecule at a particular point by recognizing a specific sequence of base pairs. Thus they are useful in forming recombinant DNA.

(c) Thermus aqtraticus-is the source of Taq-polymerase which remains active during high temperature induced denaturation of DNA in PCR technique and therefore allows chain reaction to proceed.

(a) By treating the cell with the enzyme lysozyme. 

(b) By micro injection or gene gun.

(Breaking the cell open) Treating with lysozyme.

Biotechnology is the technique of using live organisms or their cellular components like enzymes for products and processes useful to mankind. It is mainly of two types : 

(i) Traditional Biotechnology: This includes the useful processes which are based on the natural capabilities of micro organisms such as production of curd, cheese, beer, wine, vinegar etc. 

(ii) Modern Biotechnology: This includes the genetic engineering. This is based on gene manipulation and the development of the recombinant DNA technology. Production of DNA vaccine, correction of defective gene, formation of monoclonal antibodies, in-uitro fertilization are also the part of modern biotechnology.

(i) Denaturation process. 

(ii) Primers 

(iii) Taq DNA polymerase. 

Taq polymerase is a thermostable enzyme isolated from a thermophilic bacterium Thermus aquaticus. This enzyme remains functional during high temperature required for extension of DNA.

Presence of more than one recognition site will give several segments. This may complicate the gene cloning.

Shake asks are used for growing microbes and mixing the desired materials on a small scale in the lab. But the large scale production of desired bio technological product requires large stirred tank bioreactors.

Besides better aeration and mixing properties, the bioreactors have following advantages –

1. It has oxygen delivery system. 

2. It has foam control, temperature and  P control system.

3. Small volumes of culture can be with drawn periodically.