Test: Biotechnology: Principles & Processes - 1

• Plasmids renature because they have supercoiled structures that have held the two strands of the helix together during denaturation.
• Chromosomal DNA is not able to renature, however, because its longer strands have become mixed with denatured proteins.

• Insertional inactivation is the inactivation of a gene upon insertion of another gene inside in its place or within its coding sequence.
• It help in identification of recombinant clones.

• Having two antibiotic resistance genes in the same plasmid helps in identifying transformants.
• Transformants take up the plasmid and also integrate it into recombinant DNA.

• In order to use the DNA for genetic engineering processes, it must be in pure form, free from other macromolecules.
• This is termed DNA isolation and is the pioneer step. Since the DNA is enclosed within the membranes, it is required to break open the cell to release DNA along with other macromolecules such as RNA, proteins, polysaccharides, lipids, etc. and from this mixture, DNA is purified.
• A release of DNA from a cell is achieved by treating the cells or tissues with enzymes such as lysozyme (bacteria), cellulose (plant cells), chitinase (fungus), etc.
• These enzymes degrade cell wall; plasma membrane degrading enzymes like lipase, etc., are also needed. Since yeast is a fungus and fungal cell wall is made of chitin (fungal cellulose), isolation of DNA necessarily requires the use of enzyme chitinase.

• The polymerase chain reaction is a technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA.
• Calcium ions is not required in PCR technology.

• PCR is the short form for polymerase chain reaction which is the phenomenon which is used for amplification of the part-specific region of DNA as per our interest.
• The final step of PCR is extension, wherein Taq DNA polymerase (isolated from a thermophilic bacterium Thermus aquaticus) synthesises the DNA region between the primers, using dNTPs (denoxynucleoside triphosphates) and Mg²⁺.
• The primers are extended towards each other so that the optimum temperature for this
  polymerisation step is 72^∘C. Taq polymerase remains active during high temperature induced denaturation of double stranded DNA.

In agarose gel electrophoresis, the DNA fragments separate out (resolve) according to their size or length because of the sieving property of agarose gel. It means, the smaller the fragment size, the farther it will move.

Restriction enzymes are also called 'molecular scissors' as they cleave DNA at or near specific recognition sequences known as restriction sites. These enzymes make one incision on each of the two strands of DNA and are also called restriction endonucleases.

• All the enzymes at higher temperature become inactive.
• Denaturation is done at high temperature as it leads to breaking down of hydrogen bonds between the bases of polynucleotides.

Genetic engineering involves:
(i) Identifying DNA with desirable genes.
(ii) Introduction of identified DNA into the host.
(iii) Maintenance of introduced DNA in the host.
(iv) Transfer of DNA in its progeny.

Hence, option C is correct.

• Origin of replication is the specific DNA sequence on chromosome that which is responsible for initiating replication.
• Origin of replication is essential for replication of particular DNA segment.

The groups of letters that form same words when read both forward and backward are called Palindrome. For example MALYALAM which read same from both side.

The Enzymes used to join foreign DNA to plasmid is ligases. The plasmid of bacteria replicate this DNA strands along with other which can be further transferred to target cells.

The separated DNA fragments can he visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to ultraviolet radiation (we cannot see pure DNA fragments in the visible light and without staining).

EcoRI comes from Escherichia coli RY 13. In EcoRI, the letter ‘R’ is derived from the name of strain.

The separated DNA fragments can be visualized only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation. We can see bright orange coloured bands of DNA in aethidium bromide stained gel exposed to UV light.

• In gel electrophoresis, DNA molecules moves towards positively charged anode because DNA is negatively charged molecules.
• The molecules separate out due to difference in molecular weight.

• Rop genes in pBR322 codes for protein involved in replication of plasmid.
• Plasmid are able to take the foreign gene and to be transferred to target cells.

DNA is coated with tungsten before used in biolistic gun for inserting the DNA directly into target cells for obtaining particular protein.

Bioreactor is used to produce large scale production. Bioreactor is a large vessels in which large scale raw materials are biologically converted into specific products.

• Bioreactors are used to obtain biological products on large scale continually for commercial purpose.
• The sparged stirred tank bioreactor is advantageous over the simple stirred tank bioreactor as air bubbles enhance the oxygen transfer area.

The X-gel will be converted into a coloured product when B-galactosidasse acts on it.

• Blades in a bioreactor help in mixing of all the components and prevent their settling at the bottom of reactor tank.
• It also increases the oxygen level in bioreactor.

The restriction sites of the nucleoid are methylated because it protects bacteria from its own enzymes.

• A ladder is used in Gel electrophoresis as it helps in comparing the size of the DNA fragment.
• The fragments get separated from each other on the basis of molecular weight of the fragments.