31 Years NEET Previous Year Questions: Biotechnology: Principles & Processes - Grade 12 MCQ

The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation (you cannot see pure DNA fragments in the visible light and without staining). You can see bright orange coloured bands of DNA in a ethidium bromide stained gel exposed to UV light.

A hybridization probe is a fragment of DNA of variable length which is used in DNA samples to detect the presence of nucleotide sequence (the DNA target) that are complementary to the sequence in the probe. The probe hybridize to single–stranded DNA whose base sequence allow probe target base-pairing due to complementary between the probe and target.

The blue-white screen is a screening technique that allows for the rapid and convenient detection of recombinant bacteria . This technique is based on the insertional inactivation of the β-galactosidase gene.
Cells transformed with vector containing the recombinant DNA contain an inactive form of the β-galactosidase gene and hence produce white colonies.
cells transformed with non-recombinant plasmid i.e. only the vector, have an active β-galactosidase gene and thus produce blue colonies.

DNA fragments generated by restriction endonucleases in a chemical reaction can be separated by gel electrophoresis. Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. The DNA fragments separate according to their size through sieving effect provided by matrix.

A palindromic sequence is a nucleic acid sequence (DNA or RNA) that is the same whether read 5' (five-prime) to 3' (three prime) on one strand or 5' to 3' on the complementary strand with which it forms a double helix.
5. - GAATTC - 3.
3. - CTTAAG - 5.
It is a palindromic sequence of DNA cut by restriction enzyme ECORI.

PCR or polymerase chain reaction is the technique employed for the amplification of the gene of interest. The image shows 3 steps of the PCR cycle, namely denaturation, annealing, and extension. Part A represents the step of denaturation, where the dsDNA is divided into two ssDNA under high temperature. For denaturation to occur, an approximate temperature of 90-92oC is required.

Whereas, part B represents the attachment of short oligonucleotide sequences called primer by a process called annealing and part C represents the extension of the DNA segment by the addition of nucleotides by the action of the thermostable polymerase called Taq polymerase. 

Antibiotics are powerful medicines that fight bacterial infections. They either kill bacteria or keep them from reproducing. In genetic engineering, the antibiotics are used as selectable markers.

Biolistic it is direct gene transfer red method for constructing recombinant DNA. The gene gun was invented by John C. Sanford with Edward Wolf. A gene gun can be used to genetically infect cells or whole organisms with foreign DNA by aiming the barrel of the gun and firing. The microshot projectiles in the biolistic gene gun are made of microscopic (or nano) sized gold or platinum powders. These expensive powders are soaked in DNA or RNA (in raw or plasmid form) that are engineered for insertion into the genome of the cells or organisms under the gun.

For gene transfer in to the host cell without using vector microparticles made of tungsten and Gold coated with foregin DNA are bombarded into target cells at a very high velocity.

The name of this DNA polymerase is Taq polymerase extracted from a thermophilic bacterial.

A single strand DNA or RNA tagged with radioactive molecule that is used in of  hybridization of DNA or RNA is called probe.

PCR and RFLP are the methods used for genetic fingerprinting. DNA fragmentation plays an important part in forensics, especially that of DNA profiling. Restriction fragment length polymorphism (RFLP) analyses the variable lengths of DNA fragments which are formed from the digestion of a DNA sample with a restriction endonuclease. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. In polymerase chain reaction (PCR), This sample DNA is amplified from a single copy to millions of copies of DNA. It used to amplify a specific region of a DNA strand. Most PCR methods amplify DNA fragments of between 0.1 and 10 kilo base pairs (kb), although some techniques allow amplification of fragments up to 40 kb in size.
 

In pBR 322

ori - represents site of originor replication rop-represents those proteins that take part in replication of plasmid. Hind III, EcoRI- Recoginition sites of Restriction endonucleases amp^R and tet^R - They are antibiotic resistant gene part

Bacillus thuringiensis produces a large amount of crystalline protein during sporulation. In the cell toxins are formed along with the spore and are referred to as parasporal body. The bacteria are capable of entering the insect’s blood and using the host insect to reproduce. The proteins from ingested spores are activated by gut, high pH and the polypeptide toxins destroy gut epithelial cells and kill the pest.

In gel electrophoresis agarose extracted from sea weed used as gel garose, made of 0.7% gel show good resolution of large DNA and 2% gel will show good resolution of small fragments.

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

Restriction endonucleases are enzymes that makes cuts at specific positions within the DNA molecule. They acts as molecular scissors. They recognise specific base sequence at palindrome sites in DNA duplex and cut its strands.

DNA or RNA segment tagged with a radioactive molecule is called Probe. They are used to detect the presence of complementary sequences in nucleic acid samples. Probes are used for identification and isolation of DNA and RNA.

A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Restriction enzymes recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA. Many of them are palindromic, meaning the base sequence reads the same backwards and forwards. Recognition sequences in DNA differ for each restriction enzyme, producing differences in the length, sequence and strand orientation (5' end or the 3' end) of a sticky-end of an enzyme restriction. If we cut the DNA with EcoR1, the DNA would be cut right in the middle. All the pieces would be the same size, which would be 15 kb long.

Option C Hence 5' GAATTC 3' ; 3' CTTAAG 5' palindrome sequence can be easily cut at about the middle by EcoR1 enzyme.

Retrovirus as has the ability to transform normal cells into cancerous cells. Hence, it can used as a vector for cloning desirable genes into animal cells.

Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. During the process, the primary effluent is taken to aeration tank that contain large number of aerobic heterotrophic microbes. They form flocs that digest a lot of organic matter. As the biological oxygen demand of waste water is reduced, it is passed into settling tank to undergo sedimentation. The sediment of the settling tank is called activated sludge that is a rich source of aerobic bacteria. Hence, the statement
(d) is correct.
Biogas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. It is made up of methane, carbon dioxide with traces of nitrogen, hydrogen sulphide and hydrogen.
Methanobacterium is an anaerobic bacterium that is found in rumen of cattle and is helpful in the breakdown of cellulose.

Direct gene transfer is the transfer of naked. DNA into plant cells but the presence of rigid plant cell wall acts as a barrier to uptake. Therefore protoplasts are the favoured target for direct gene transfer. Polyethylene glycol mediated DNA uptake is a direct gene transfer method that utilizes the interaction between polyethylene glycol, naked DNA, salts and the protoplast membrane to effect transport of the DNA into the cytoplasm.

The linking of antibiotic resistance gene with the plasmid vector became possible with DNA ligase. DNA ligase is an enzyme that is able to join together two portions of DNA and therefore plays an important role in DNA repair. DNA ligase is also used in recombinant DNA technology as it ensures that the foreign DNA is bound to the plasmid into which it is incorporated. 

Gel electrophoresis is a technique to separation of DNA fragments according to their size. DNA is negatively charged so in gel tank when electric passed, DNA move towards positive electrode. 

Plants developed by genetic engineering are called transgenic plants or genetically modified crops from which genetically modified food is produced. For their production micro-organisms (bacteria, virus) are used. So, by consuming them there is a danger of entry of viruses and toxins causing differ types of allergies and other health hazards to human beings.